First lets start with calculating how much 2kg of oranges cost (we do this by cross multiplying):so if 3kg = £54 2kg = £xto determine the value of x, we can write the following equation:3x = 5423x = 108x = 108/3x = £36.Now we must calculate the cost of buying 7kg of apples. We do this using the same method:5kg = £607kg = £yto determine the value of y, we can write the following equation:5y = 6075y = 420y = 420/5y = £84.Therefore, the total amount Nina pays for 7kg of apples and 2kg of oranges is:total = x + ytotal = £36 + £84total = £120.