Negatives Inside

Negative numbers follow the same order as every other number; each step just brings its sign rule along. Take $-2 \cdot \left(5 - 9\right)$. Parentheses first: $5-9$ is -4. Then the product: $-2 \cdot \left(-4\right)$ is 8, because two negatives multiply to a positive.

When a line holds several products, work them all out before the sums. In $6 \cdot \left(-3\right) - 4 \cdot \left(-5\right)$ the products are -18 and -20, so the line is $-18 - \left(-20\right)$. Subtracting a negative is adding its opposite, so you can write that straight away as $-18+20$, which is 2.

Doing the products first matters. Going left to right instead would subtract 4 from -18 and then multiply the result by -5, which gives 110, nowhere near 2.