1. work out the balance for £4500 invested for 2 years at 4% per annum 2. in a ‘20% off’ sale, a coat was £220. work out the original price.

1.
I am guessing this is for simple interest.
S.I = PRT
P for Principal Amount
R for Rate 
T for Time in years
I = £4500 × 0.04 × 2
(0.04 =  = 4%)
I = £360
The total amount will be 4500 + 360 = £4860

2. 20% off, £220
Original price?
original price × 0.2 = 220
(0.2 =  = 20%)
Divide by 0.2 on either sides to find the original price

0.2 and 0.2 cancels out
original price = £1100

check:
0.2 × 1100 = £220

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