let

s = Sandy's today's age

w = his wife's age

d = his daughter's age

Sandy is 5 years older than his wife

s = w + 5

his wife is 5 times as his daughter

w = 5d

before 3 years the age of his daughter was 4 years

d - 3 = 4

d = 4 + 3

d = 7

then w = 5*7 = 35 and finally s = 35 + 5 = 40.

Sandy is 40 years old now.