The quotient of c and −19 is 38.

-2

Step-by-step explanation:

When you multiply a negative by a negative, it always becomes a positive. So, if you multiply -19 by -2, you would get 38, meaning the c=-2.

∠acb = 8°

step-by-step explanation:

∠xba lies on the circle and is half the measure of the intercepted arc ax

hence

measure of arc ax = 2 × 42° = 84°

∠acb is outside the circle and is

∠acb = (arcab - arcax ), hence

∠acb = 0.5 (100 - 84) = 0.5 × 16° = 8°