72 is equal to 80% of a number n. write and solve and equation to find n. write the percent as a decimal {show work}

A(t)=728(1+0.04)^t how much money did aditya originally invest

Does anyone know how to solve and graph this: 4 + | a + 2 | < 7the only part i don't get is the "4 +"

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.