Please help me out, thank u so much!

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

Acompany produces packets of soap powder labeled “giant size 32 ounces.” the actual weight of soap powder in such a box has a normal distribution with a mean of 33 oz and a standard deviation of 0.7 oz. to avoid having dissatisfied customers, the company says a box of soap is considered underweight if it weighs less than 32 oz. to avoid losing money, it labels the top 5% (the heaviest 5%) overweight. how heavy does a box have to be for it to be labeled overweight?

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.