Why is it mathematical true that you can set the two products that result from cross multiplying equal to each other

Need plz been trying to do it for a long time and still haven’t succeeded

Urgent? will give brainliest given that the blue triangle is a right triangle, which expression correctly gives the area of the red square? a) a2 + b2 b) a2 - b2 c) a2 - c2 d) c2 - a2

Twice the sum of a number and 2 is equal to three times the difference of the number and 8. find the number.