Question 989680
.
J=Jen's age=80 years; M=Mark's age=5 years; 
x=years until Jen is 4 times Mark's age
.
J+x=4(M+x)
80+x=4(5+x)
80+x=20+4x
60=3x
20=x
ANSWER: Jen will be 4 times Mark's age in 20 years.
.
CHECK:
J+x=4(M+x)
80+20=4(5+20)
100=4(25)
100=100