the sum of the present age of a father and his son is 40 years 4 years has father will be three times as old as his son will be find their present age​

Let’s define our variables:

D = dad’s age now

S = son’s age now

Given:

D=4S now

D+4=3(S+4) in 4 years

We can expand the second equation:

D+4=3S+12

D=3S+8

And we can subtract it from D=4S

D=4S-(D=3S+8)

0=S-8

S=8 the son’s age now.

D=4S=4(8)=32 the father’s age now

Check:

32+4=3(8+4)

36=3(12)

36=36 Check

I hope this helps you

problem:

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

f(5/2) = 10/3

i hope this !