Mark gave 21 tadpoles to his threes friends . mark gave twice as many tadpoles to david as his did chris . george received twice as many tadpoles as david . how many tadpoles did each friend receive?

Find the volume of the described solid.the solid lies between planes perpendicular to the x-axis at x = 0 and x=7. the cross sectionsperpendicular to the x-axis between these planes are squares whose bases run from the parabolay=-31x to the parabola y = 30/x.a) 441b) 147c) 864d) 882

Use the elimination method to solve the systems of equations.choose the correct ordered pair. 7x+4y=39

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.