Jane made a door frame for the house but does not have a tool to measure the angles. How can she check that
the corner is 90 degrees?

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.

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in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

hope it