How do you subtract fractions with different denominators?

The class wants to raise a total of $750.if they receive a profit of $1.25 from each candybar sold, how many bars must they sell to reachtheir goal

Alake near the arctic circle is covered by a 222-meter-thick sheet of ice during the cold winter months. when spring arrives, the warm air gradually melts the ice, causing its thickness to decrease at a constant rate. after 333 weeks, the sheet is only 1.251.251, point, 25 meters thick. let s(t)s(t)s, left parenthesis, t, right parenthesis denote the ice sheet's thickness sss (measured in meters) as a function of time ttt (measured in weeks).

Is the power produced directly proportional to the wind speed, give reasons for your answer?