I'm not sure if understand the question correctly but the way I understand the question:
The sum of angles on one side of trapezoid equals 180.
10x+7+(6x-3)=180
10x+7+6x-3=180
16x=176
x=11
Then one angle: 117 the second one 66-3=63
;) Right I read longer base but the question is larger angle so it is definitely 117 so C is the answer.