Find the lcd for each pair of fractions
3/4, 5/8
3/4, 1/12
1/6, 5/24
2/9, 1/6
1/4, 3/7
1/12, 7/24
2/5, 1/2
1/16, 3/8
8/9, 1/5

∠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°