Can someone help me solve this? I’m not sure what to do

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

Use the quadratic formula to solve the equation. if necessary, round to the nearest hundredth. x^2 - 8 = -6x a. –7.12, 1.12 b. 7.12, –1.12 c. 7.12, 1.12 d. –7.12, –1.12

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle