This is a proportion question, so you're going to create two ratios, set them equal to each other, and solve for x. The question tells us that a 6in drawing is actually 42ft, so we'll write that as (6in/42ft).
Then, we'll create a second proportion using the rest of the information in the question. We know the drawing is 7in, and we're solving for how tall the flag pole is in ft. We want this proportion to mirror our first proportion, so we'll write this as (7in/xft).
We then set the two proportions equal to each other:
6in = 7in
42ft x ft
Then we solve algebraically:
6x = 42*7
6x = 294
divide both sides by 6
x = 49
Once you carry down the units, you learn the flag pole is 49 ft tall.