Salut!
a × b = 300
b = c × 5
c = d - 21
d = e ÷ 6
e ÷ 9 = 18
e = 18 × 9
e = 162
d = e ÷ 6 => d = 162 ÷ 6
d = 27
c = d - 21 => c = 27 - 21
c = 6
b = c × 5 => b = 6 × 5
b = 30
a × b = 300 => a × 30 = 300
a = 300 ÷ 30
a = 10
