Answer:
Use this pencentage change formula:
New - Old
---------------- x 100
Old
Step-by-step explanation:
390 + 35.10 = 425.1 (New value)
So apply this to the formula:
425.1 - 390
--------------- x 100
390
<em>Which is = 9%</em>
<em>Hope</em><em> </em><em>it</em><em> </em><em>helps</em><em>.</em><em> </em><em>Cheers</em><em>!</em><em> </em><em>:</em><em>)</em>
Answer:

Step-by-step explanation:

1. set the equation for the area of each shape equal to each other
2. simplify each side until you get 
3. subtract 16 from both sides which will give you 
4. subtract 3x from both sides which will give you the value of x. 
5. check that
is correct by plugging it into the equations
triangle:

rectangle:

the areas are the same
This is it! remember that it is undefined because you can't divide by 0.