You probably jsut need to use law of cosines in order to solve for angle A

or
If a coral reef grows at a steady rate every week, then to find how much it grows in 12 weeks, we need to multiply the growth rate by 12 weeks. Also, since we want our answer in centimeters, we can change the growth rate to centimeters. 0.15m = 15cm
15cm * 12 = 180cm
The coral reef will grow 180cm in 12 weeks.
I think the answer was a option c
(a) The dimensions of the base of the box are (8 -2x) and (10 -2x). The depth of the box is x. The volume is the product of these dimensions.
V = x(8 -2x)(10 -2x)
(b) A graphing calculator is suitable "technology". The process is ...
• write the equation in the calculator
• adjust the scaling so the curve fills the display area
• select the maximum point to reveal its coordinates
The value of x that maximizes box volume is about 1.5 inches.
Answer:
First subtract 7 from each side of the equation
Step-by-step explanation:
2x+7 = 13
First subtract 7 from each side of the equation
2x+7 -7 = 13-7
2x = 6
Next divide each side by 2
2x/2 = 6/2
x=3