In a mixture of concrete, there are four lbs of cement mix for each pound of gravel. if the mixture contains a total of 130 lb of these two ingredients, how many pounds of gravel are there?

How to do this , and can some one explain

Kayla and alberto are selling fruit for a school fundraiser. customers can buy small boxes of grapefruit and large boxes of grapefruit. kayla sold 3 small boxes of grapefruit and 1 large box of grapefruit for a total of $65. alberto sold 1 small box of grapefruit and 1 large box of grapefruit for a total of $55. what is the cost each of one small box of grapefruit and one large box of grapefruit?

In an isosceles triangle, the vertex angle is 112 degrees. what is the measure of each base. a.34 b.24 c.44 d.54