Answer: [tex]35^{\circ}[/tex]
Step-by-step explanation:
Angles ACB and DCA add to form angle ACB, which is a right angle, so:
- 6y - 7 + 8y - 1 = 90 [angles that add to form a right angle add to 90 degrees]
- 14y - 8 = 90 [combine like terms]
- 14y = 98 [add 8 to both sides]
- y = 7 [divide both sides by 14]
So, [tex]m\angle ACB=6(7)-7=\boxed{35^{\circ}}[/tex]
