My original answer was wrong and was corrected by Eric Barnes.
Remember BIDMAS (UK) or PEMDAS (US) which sets out the order of operations.These stand for
So 6(-3) + 12/(-2) + 4
= -18 + (-6) + 4 = -8 + 4 = -20.
12 plus 63 is 75.
12 minus 63 plus 9 is -42
12
5.25
12 + 15 + 63 + 12 + 24 + 34 + 23 + 15 = 198
12.6
63/10 + 100 = 106.3
-4
3. 63 ÷ 5 = 12 r 3
63 + (12 x 15) = 63 + 180 = 243
12.6
63