# SAT Math Multiple Choice Practice Question 480: Answer and Explanation

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**Question: 480**

**21.**

In the figure above, *x* || *y*. What is the value of *a* in terms of *b* and *c* ?

A. *b + c*

B. 2*b* – *c*

C. 180 – *b* + *c*

D. 180 – *b* – *c*

E. 360 – *b* – *c*

**Correct Answer:** D

**Explanation:**

**D** Don't forget that you can plug in on geometry questions. Let's make *b* = 70° and *a* = 30°. So the third angle in the triangle is 80°. You know that *c* would be 80°, because it is opposite an 80° angle. Your target answer is a = 30°, so plug in 80° and 70° to find it. The only possible answer is D.