中二數學一條【求完整說明及回答】

let sam's age be x and the age of his father be y,

4x+3=y..(i)

(x-3)+(y-3)=47..(ii)

from(ii):
x+y=53
y=53-x..(iii)

put(iii) into (i)

4x+3=53-x
5x=50
x=10

put x=10 into (ii)
y-3=40
y=43

sam is 10 years old and his father is 43 years old now.