Angles cap x and cap y are supplementary. Angle cap x is 3 times the measure of angle cap y What is the measure of angle cap x ?

Supplementary angles add up to 180 degrees. Since angle x is 3 times angle y, together they make 3 equal parts plus 1 equal part, or 4 parts; each part is 180 ÷ 4 = 45 degrees. Thus angle x is 3 × 45 = 135 degrees, choice B.

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