a: =17x100-120=1700-120=1580
a) \(17\cdot85+15\cdot17-120\)
\(=17\cdot\left(85+15\right)-120\)
\(=17\cdot100-120\)
\(=1700-120\)
\(=1580\)
b) \(27\cdot77+24\cdot27-27\)
\(=27\cdot\left(77+24-1\right)\)
\(=27\cdot100\)
\(=2700\)
c) \(2^3\cdot17-2^3\cdot14\)
\(=8\cdot17-8\cdot14\)
\(=8\cdot\left(17-14\right)\)
\(=8\cdot3\)
\(=24\)