Question

Mark' s age plus three times Nik's age is equal to 54. Twice Mark's age plus four times Nik's age is equal to 80. How old is Nik?

Answer 1

Nik's age: x


Here is a system of equations that we can set up based on the information...
x+3y=54
2y+4x=80

Rearrange these...
x+3y=54
4x+2y=80

x+3y=54 solve an equation for y
4x+2y=80
2y=80-4x
y=40-2x

Plug in 40-2x for y in the other equation...
x+3(40-2x)=54
x+120-2x=54
-x+120=54
-x=-66
x=66

Nik is 66 years old.

Hope this helps! Best wishes:)