Since the average high temperature is 65
Average = sum / n
N = no of days
n = 5
65 = 76 + 70 + x + 68 + 55 / 5
Introduce cross multiplication
65 * 5 = 76 + 70 + x + 68 + 55
325 = 269 + x
Make x the subject of the formula
x = 325 - 269
x = 56
The answer is 56