Write an expression that represents the area of only the red shaded region in terms of x

1st find the area of bigger rectangle ie l×b

again find area of small rectangle ie l×b

now subtract area of small rectangle by bigger one you get the area of shaded part

answer: 8 years

step-by-step explanation:

the explanation is that in 8 years the child will be 20 and in 8 years the father will be 40 and 20 is half of 40.