Question

Jack is 27 years older than Susan. In 5 years he will be 4 times as old as she is. Find the present ages of jack and Susan

Answer 1

X - Jack's age
y - Susan's age

Jack is 27 years older than Susan.
$x=y+27$

In 5 years he will be 4 times as old as she is.
$x+5=4(y+5)$

The system of equations:
$x=y+27 \\ x+5=4(y+5) \\ \\ \hbox{substitute y+27 for x in the 2nd equation:} \\ y+27+5=4(y+5) \\ y+32=4y+20 \\ y-4y=20-32 \\ -3y=-12 \\ y=\frac{-12}{-3} \\ y=4 \\ \\ x=y+27=4+27=31$

Jack is 31 years old and Susan is 4 years old.