In both cases, you make use of the relationship between the length and width of a rectangle and its area. We take for granted that you are comfortable with arithmetic using mixed numbers and/or fractions. The applicable formula for the area (A) of a rectangle in terms of its length (L) and width (W) is ...
A = L·W
Fill in the given values and solve for the remaining one.
1.
3/4 in² = (2/3 in)·W . . . . . divide by the coefficient of W to find W.