Answer:
x = 10
Step-by-step explanation:
In similar polygons, the lengths of the sides are proportional.
(3x + 5)/42 = 30/36
(3x + 5)/42 = 5/6
6(3x + 5) = 5 × 42
18x + 30 = 210
18x = 180
x=10
7.
[tex]\frac{3x+5}{42} =\frac{30}{36} \\3x+5=\frac{30}{36} \times 42\\3x+5=35\\3x=35-5=30\\x=\frac{30}{3} =10[/tex]
