Andy estimated that he would need 79 feet of lumber for a tree house project. he later found that the actual amount of lumber needed was 68 feet. what was the percent error of andy's estimation?

Step-by-step explanation:

79 divided by 68 is your answer

You can do the math

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

answer: the answer for that is 22/3