Question 1154263
let m = my age
let s = sister's age
:
Write an equation for each statement
:
 twice my age plus three times my sister's age is 86.
2m + 3s = 86
 Three times my age plus four times my sister's age is 120.
3m + 4s = 120
:
multiply the 1st equation by 3, the 2nd equation by 2
6m + 9s = 258
6m + 8s = 240
----------------subtraction eliminate m, find s
0 + s = 18 yr is sisters age
:
 How old am I?
2m + 3(18) = 86
2m + 54 = 86
2m = 86 - 54
2m = 32
m = 32/2
m = 16 yr is my age
:
:
Check solutions in 2nd equation
3(16) + 4(18) = 
48 + 72 = 120