The three angles of a triangle are A, B, and C, and the degree of angle A is four times greater than that of angle C by 20 degrees, and the degree of angle C is twice that of angle B. What is the degree of angle A?
一个三角形的三个角分别为A、B、C，其中角A度数的4倍比角C多20度，角C度数是角B的两倍，则角A的度数为多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">180 - 5</gadget>
<output>175</output>

<gadget id="calculator">(1/2) + 1 + 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">175 / (7/2)</gadget>
<output>50</output>

<gadget id="calculator">(1/2) * 50</gadget>
<output>25</output>

<gadget id="calculator">25 + 5</gadget>
<output>30</output>

<result>30</result>