How do I solve 6/11 + 1/2 - 1/5

The probability of winning something on a single play at a slot machine is 0.11. after 4 plays on the slot machine, what is the probability of winning at least once

Find the value of 1715⋅211.though these numbers aren't quite as nice as the ones from the example or the previous part, the procedure is the same, so this is really no more difficult. give the numerator followed by the denominator, separated by a comma.

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?