Question 618733
Well, if the older person was 8 when you were born and you want to know how old you are when both ages add up to 150:

You are correct in your equation:
x + (x + 8) = 150

you need to rearrange to find x:

so you put the x's on one side and numbers on the other. Remember if you move something to the other side of the equation you change the sign (unless you are just switching everything)

So:

x + x + 8 = 150
x + x = 150 - 8
2x = 142

to find x you need to divide both sides by 2 to change the 2x to x:

2x/2 = 142/2
x = 71

so you are 71 and the older person is 71+8 = 79



For an equation stating that the older person is 3 times the younger person. If you are still using the same i.e. x + 8 for the older person:

Then 3x = x + 8

both sides of the equation represent the age of the older person. At the same time they are three times your age but they are still 8 years older at the same time so both equations (3x and x+8) are equal to each other.

so if 3x = x + 8
rearrange as before:

3x - x = 8

2x = 8

2x/2 = 8/2

x = 4

and they would be x + 8 i.e. 4 + 8 = 12