Question 852451
2S - 4 = F
F = 40
.
Simply substitute the value of F from the second equation into the first.
2S - 4 = 40
Add 4 to each side
2S = 44
Divide b 2
S = 22
.
Let's prove it.
Twice the age of the son (22 * 2 = 44) is 4 years older than his father (40).
44-4=40
success!