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87x101=(100x87)+(1x87)=8700+87=8787
12x15,3=(10x15,3)+(2x15,3)=153+30,6=183,6
999x32=(1000x32)-(1x32)=32000-32=31968
98x2,4=(100x2,4)-(2x2,4)=240-4,8=235,2
8x(6+x)=48x+8x²
7x(5-a)=35x-7ax
(15+b)x=15x+bx
x(12-y)=12x-xy
7x(m+8)=7xm+56x
(15+b)xa=15xa+abx
9(x-8)=9x-72
n(n-16)=n²-16n
12x15,3=(10x15,3)+(2x15,3)=153+30,6=183,6
999x32=(1000x32)-(1x32)=32000-32=31968
98x2,4=(100x2,4)-(2x2,4)=240-4,8=235,2
8x(6+x)=48x+8x²
7x(5-a)=35x-7ax
(15+b)x=15x+bx
x(12-y)=12x-xy
7x(m+8)=7xm+56x
(15+b)xa=15xa+abx
9(x-8)=9x-72
n(n-16)=n²-16n