<h3>
Answer: choice B) 36</h3>
=================================================
Explanation:
The vertical sides, when read from left to right, can be divided to get this fraction: 9/90
Following the same order and direction, we divide the slanting corresponding sides to get: b/360
The fractions we constructed are equal to one another, as the triangles are said to be proportional.
We have the fraction 9/90 = b/360
Lets cross multiply and solve for b
--------------------
9/90 = b/360
9*360 = 90*b
3240 = 90b
90b = 3240
90b/90 = 3240/90
<h3>b = 36</h3>
--------------------
A quick way to do this may be to notice how the jump from 9 to 90 is "times 10" so the jump from b to 360 is also "times 10". Think in reverse to divide 360 over 10 and we land on 36 as our answer. This line of thinking does not work as simple for all proportional problems.
Start by combing like terms. You will get 3x+12=51. Now subtract 12 from both sides (3x=39). Divide both sides by 3 (x=13). The answer is 13.
