36a^2− 169x^2 factorized

Which ordered pair (c,d) is a solution to the given system of linear equations- c+2d=13 -9c-4d=-15

0if x and y vary inversely and y=6 as x=7, what is the constant of variation?

When you have 25 numbers, and jake picks 3 random numbers and puts them back, what is the chance bob has of picking those 3 numbers when he picks 6 random numbers (without putting them back)? explain.