Question

(37-7). (-9) + (-17-13).21

Answer 1

\(\left(37-7\right).\left(-9\right)+\left(-17-13\right).21=30.\left(-9\right)+\left(-30\right).21\)

\(\Leftrightarrow\left(-9-21\right)\left(30\right)=-30.30=-900\)

Answer 2

\(\left(37-7\right)\cdot\left(-9\right)+\left(-17-13\right)\cdot21\)

\(=30\cdot\left(-9\right)+\left(-30\right)\cdot21\)

\(=-30\cdot9+\left(-30\right)\cdot21\)

\(=-30\left(9+21\right)=-30\cdot30=-900\)