The sum of 2 numbers is 120.if the larger number is four times the smaller number, what are the two numbers?

Lets call the two numbers a and b.

We know that a+b=120.
We also know that a=4*b, because the larger number is 4 times the smaller number.
Therefore, if a=4*b, we can change a+b=120 to:
4*b+b=120, 
5b=120
b=120/5
b=24

We can than sub b=24 back into a+b=120
a+24=120
a=120-24
a=96

Therefore, the two numbers are 24 and 96.

A + b=120

4a + a=120
5a=120
a=120/5
a=24

24x4=b
b=96

a=24 b=96