I cheated now I need to know how to “check “ it and how’d I get this answer

The isosceles triangle has two sides of equal length, a, that sre longer than the length of the base ,b. the equation 2a+b=15.7 can be used to find the sides length. if one of the longer sides is 6.3 centimeters what is the length of the base

Given that abcd is a rhombus, what is the value of x?

Select all the expressions that will include a remainder.