First, multiply $3 by 4 to get $12 spent on cookies. Then, you multiply $12 by 2 to know that the pies cost $24. You then divide the $24 by 3 to get $6 per pie. Meaning, each pie had cost $6. You add the $12 and $24 together to get $36. Finally, you subtract $36 from $40 to know that she only has $4 left.
Total number of computers in sample = 72 + 112 + 711 = 895.
P(LQ) = 72/895 = 0.08
P(MQ) = 112/895 = 0.125
P(HQ) = 711/895 = 0.794
The answer to number 1 is B