If this is an equilateral triangle, we need half of it to find the height which is a leg of a right triangle with a hypotenuse of 15.  That means that the base of this half triangle is 7.5.  Use Pythagorean's Theorem to fine the height.  

.  x = 12.99 or 13
 
        
        
        
Answer:
11
Step-by-step explanation:
198 ÷ 18 = 11
x = 11
......
 
        
             
        
        
        
Answer:        4x² -4
Step-by-step explanation:
First, evaluate the exponent you'll get,  + 4x² -5 then evaluate to get, 1+ 4x² -5. Next, subtract the numbers, 1 + 4x² -5 then to get, -4 +4x². Lastly, rearrange the terms,  -4 +4x² turns into, 4x² -4!
+ 4x² -5 then evaluate to get, 1+ 4x² -5. Next, subtract the numbers, 1 + 4x² -5 then to get, -4 +4x². Lastly, rearrange the terms,  -4 +4x² turns into, 4x² -4!
 
        
             
        
        
        
7 + 2x = 51
hope this helps