3.0 NOT SURE IF ITS CORRECT
Answer:
3√7
Step-by-step explanation:
9²+B²=12²
simplify
81+B²=144
minus the 81
B²= 63
For this case we have:
Cost of manufactures of T-shirts 
where x represents the number of T-shirts
Part A:
Substituting
in the total cost equation you have to:

Thus, the cost of 8 shirts will be 
Part B:
If
then

Thus, the cost of 12 shirts will be 
Answer:

3x+4=28 because 3 times an unknown number was mentioned first and mentioned together so they will be together, increased by 4 is +4 and comes after, the result of is the same as equals so you put the equals sign and whatever number they gave after.