Explications étape par étape:
a.x=2 y=1
x×4 = 1×2+(1+4)×2
=2×4 =2+5×2
=8 =2+10
=12
b.x=3
=3×4
c.x=6
=6×4
=24
y=3
=3×2+(3+4)×2
=6+7×2
=6+14
=20
d.x=10
=10×4
=40
y=7
=7×2+(7+4)×2
=14+11×2
=14+22
=36