(3+4)x9=7x9=63 , (3+4)x9=3x9+4x9=27+36=63
(6+2)x5=8x5=40 , (6+2)x5=6x5+2x5=30+10=40
7x(8+2)=7x10=70 , 7x(8+2)=7x8+7x2=56+14=70
8x(5+4)=8x9=72 , 8x(5+4)=8x5+8x4=40+32=72
7x(10-6)=7x4=28 , 7x(10-6)=7x10-7x6=70-42=28
(8-5)x4=3x4=12 , (8-5)x4=8x4-5x4=32-20=12