The answer is 20. you'll have to multiply 10 times 3 and get 30. Then you'll subtract the 10 from the 30 and get 20
Could you attach photo of a problem. It appears 2+..... =4 is missing
Solution
For this case we can use the following formula:

Where:
P= 400800 = present value
A= future value
r= 0.055 interest rate
n= 4, number of times that the interest is compund in a year (quarterly)
t= 4 years
Replacing we got:

then the interest would be:
for this case we have to define trigonometric relations of rectangular triangles, that the tangent of an angle is given by the leg opposite the angle on the leg adjacent to the angle. So:

Answer:
