I'm not sure if this is the answer so wait to see if someone else answers it. I'm just curious if I'm right later.
Answer:
51
Step-by-step explanation:
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We know that
surface area=2*[area of the base]+perimeter of the base*height
find the area of the base
is an equilateral triangle
b=15/3----> 5 in
applying the law of sines to find the area
Area=(1/2)*b²*sin 60°------> area=(1/2)*5²*sin 60°----> 10.8253 in²
alternative method to find the area of the equilateral triangle
find the h value
applying the Pythagoras theorem
h²=5²-2.5²-----> h=√18.75-----> h=4.33 in
area=b*h/2----> area=5*4.33/2----> 10.8253 in²
surface area=2*[10.8253]+15*4-----> 81.65 in²
the answer is
81.65 in²
Z=xy
dividing both sides with y to isolate x,
z/y=xy/y
z/y=x
x=z/y