1. Calculate the interest rate percent per annum for a loan of #2,720 for 4 years and a repayment of #2,856 .

1. To calculate the interest rate percent per annum for a loan, we use the formula:
Interest = Total repayment - Loan amount

Interest = #2,856 - #2,720 = #136

Interest rate percent per annum = (Interest / Loan amount) * 100
Interest rate percent per annum = (136 / 2720) * 100 = 5%

2. (a) To make v the subject of the formula E = mv/2:
E = mv/2
2E = mv
v = 2E / m

(b) When m = 2 and E = 120:
v = 2*120 / 2 = 120

3.
(a) Let y represent the age of the son. Since the father is 7 times older, the father's age is 7y. The sum of their ages is 54, so we form the equation:
y + 7y = 54

(b) Solving the equation:
8y = 54
y = 54 / 8
y = 6.75

Son's age (y) = 6.75 years
Father's age (7y) = 7 * 6.75 = 47.25 years

4. To solve the equations:
3x + 2y = 4
2x + 3y = 1

We can solve this using the elimination method:
Multiply the first equation by 3 and the second equation by 2 to make the coefficients of one variable the same:
9x + 6y = 12
4x + 6y = 2

Subtract the second equation from the first equation:
9x + 6y - (4x + 6y) = 12 - 2
5x = 10
x = 10 / 5
x = 2

Substitute x = 2 back into the first equation to find y:
3(2) + 2y = 4
6 + 2y = 4
2y = -2
y = -2 / 2
y = -1

Therefore, x = 2 and y = -1.