# Evaluate Expressions

You can start the topic in 8 second(s).
Do you want to start Evaluate Expressions and other topics without waiting? Check our remove advertising plans and support our mission to enable anyone, anywhere, and at any time, to educate themselves via standards-based interactive multimedia e-learning for free.
• Study Notes

### Pre-Algebra Mathematics - Evaluate Expressions

• Topic Reviews
Papua New Guinea 09 April 2017
Joseph L.

what is the sing of the point?

Kenya 09 April 2017
Edith N.

best when we summarize by saying we work all with the mnemonic BODMAS.(brackets ,of,division,multiplication ,addition and subtraction)workin from left to right

09 April 2017
Asia W.

hey , can someone please tell me what type of plugin?

Netherlands 08 April 2017
Anamaria Cristina T.

guys i know how to start the next topic. so, after u finish the currently topic, press 'exit course' thn press 'finish' , nd ur module is completed! c.ya!!!

Jamaica 08 April 2017
Natalee W.

can i get some help please i am unable to see the content of the topic it is saying a plug in is needed to display.. can someone please tell me what type of plugin.

Ireland 08 April 2017
Ahmed A.

08 April 2017
KimberlyCzarina B.

are there any examination after this?

United States 08 April 2017
John L.

-19??? Where did negative come from!!!

United States 08 April 2017
DeAnn C.

This person does not follow order of operations. Rather confusing when the previous module was about Order of Operations.

08 April 2017
Mackenzie C.

I think that the lesson was very easy to understand.

• Text Version

### Pre-Algebra Mathematics - Evaluate Expressions

A variable is a letter that represents unspecified numbers e.g. x, y or z.
6+x=12
To evaluate an algebraic expression you have to substitute each variable with a number and perform the operations included.
If we know the value of our variables we can substitute the variables for their values and thus evaluate the expression
Example
Calculate if x=3 and z=2
6z+4x=?
Replace x with 3 and z with 2 to evaluate the expression.
6z+4x=?
6x2+4x3=?

12+12=24

Video lesson: Evaluate the following expression for x = 2, y = 5 and z = 4
4x+(7-z)-6y

The solution can be seen in the video in the next page.
Here we have an algebraic equation rather than an expression that we want to evaluate for values of x, y and z and see what we get. The expression is 4x+(7-z)-6y. Now if we’re given values for x, z and y then we can evaluate this expression to some numerical value. We’re given x=2, z=4 and y=5. So here we have our values of x,z and y so we can just plug in our evaluate for those three values. So here we have four times two plus seven minus z is four and minus six times y which is five. Now we can just multiply these out and simplify a little bit from here. Four times two is eight, plus seven minus four is three. Minus six times five is thirty. Now we can add these, eight plus three is eleven minus thirty. Eleven minus thirty is negative nineteen.