Robbie was attempting to calculate the solution to the problem below. Are his steps of the solution correct?

Iq scores for adults age 20 to 34 years are normally distributed according to n(120, 20). in what range does the middle 68% of people in this group score on the test?

The volume of gas a balloon can hold varies directly as the cube of its radius. imagine a balloon with a radius of 3 inches can hold 81 cubic inches of gas. how many cubic inches of gas must be released to reduce the radius down to 2 inches?

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way