Answer:
The correct answer is 18
the correct expression is 
Step-by-step explanation:
let the number be n
therefore if he is required to multiply n by 4 and added to 6 we have

given that he did otherwise by adding 6 to n and multiply by 4 we have

Firstly we need to solve for n in equation 2

Dividing both sides by 4 we have

In order to solve for the correct answer let us input n=3 in equation 1 we have

Answer:
72 Centimeters
Explanation:
Formula for area: 1 /2 b · h
b = Base (18 cm.)
h = height (8 cm.)
1 / 2 Base: 9
height: 8
9 · 8 = 72
Therefore the area of the triangle is 72 centimeters