Question 997076
x,  Ali's age
y,  Father's age


{{{system(y-7&1/2=5(x-7&1/2),y+7&1/2=2(x+7&1/2))}}}


{{{system(y-7&1/2=5x-37&1/2,y+7&1/2=2x+15)}}}


{{{(y-7&1/2)-(y+7&1/2)=(5x-37&1/2)-(2x+15)}}}---------obviously using elimination method;  you finish this.