a-5×5×4 = b×10 = c:2:2 = 600:d = 10×2×5
a - 100 = b×10 = c : 2 : 2 = 600 : d = 100
d = 600 : 100 = 6
c : 2 :2 = 100
c :2 = 100×2
c : 2 = 200
c = 200×2
c = 400
b × 10 = 100
b = 100 : 10 = 10
a - 100 = 100
a = 100 + 100 = 200
a = 200
b = 10
c = 400
d = 6
c × d - a × b = 400×6 - 200×10 = 2 400-2 000 = = 400
