Question 335851
Sarah be x years
John = 3x years
..
last year
sarah was x-1
John was 3x-1
..
3x-1=4(x-1)
3x-1=4x-4
add 1 to both sides
3x+1-1=4x+1-4
3x=4x-3
add -4x to both sides
3x-4x=4x-4x-3
-x=-3
divide by -1
x= 3
sarah = 3 years
John = 3x = 9 years