9514 1404 393
Answer:
Step-by-step explanation:
The marked angles form a linear pair, so have a sum of 180°.
(4a +10) +(6a) = 180
10a = 170 . . . . . . . . . . subtract 10
a = 17 . . . . . . . . . . . . . divide by 10
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Then the measure of angle ABC is ...
∠ABC = 4a +10 = 4(17) +10 = 68 +10 . . . . . substitute 17 for 'a'
∠ABC = 78°
