Estimate the answer of the following calculation by rounding to the nearest whole number.

$\frac{7.38}{-1.86}$

Estimate the answer of the following calculation by rounding the numbers.

$-53\times 39$

Estimate the answer of the following calculation by rounding the numbers.

$32\times -61$

Estimate the answer of the following calculation by rounding the numbers.

$-38\times 9.3$

Estimate the answer of the following calculation by rounding the numbers.

$493÷-5.1$

Work out the following calculation, start by doing the brackets first.

$3\times (-6+2)$

Work out the following calculation, start by doing the brackets first.

$-4\times (-1+7)$

Work out the following calculation, start by doing the brackets first.

$5\times (-2-4)$

Work out the following calculation, start by doing the brackets first.

$2\times (3--7)$