Question 170802
call fathers age f and daughters age d
:
f=4d....eq 1
f+20=2(d+20)..eq 2
:
take f's value from eq 1 and plug it into eq 2 and distribute the right side of eq 2

:
4d+20=2d+40
:
2d=20
:
{{{highlight(d=10)}}}daughters age
{{{highlight(f=4(10)=40)}}}fathers age