Step-by-step explanation:

Answer:
b = 10
Step-by-step explanation:
The area (A) of a triangle is calculated as
A =
bh ( b is the base and h the height )
Here h = 3x + 15 and A = 15x + 75, thus
× b × (3x + 15) = 15x + 75
Multiply both sides by 2 to clear the fraction
b(3x + 15) = 30x + 150
Divide both sides by (3x + 15)
b =
← factor numerator and denominator
=
← cancel the factor (x + 5) on numerator/denominator
= 
= 10
X is less than or equal to $30, she can spend $30, she cant spend more, she can spend less.
The answer should look like X<30 with a line under the less than sign, i hope this helps.