Can someone help me solve this I do not understand it

Solve the system of equations. y= 2x y= x^2 - 15

Will give brainliest what is the value of x? enter your answer in the box.

Solve the problem. a student earned grades of c, a, b, and a in four different courses. those courses had these corresponding numbers of credit hours: 4, 5, 1, and 5. the grading system assigns quality points to letter grades as follows: a = 4, b = 3, c = 2, d = 1, and f = 0. compute the grade point average (gpa) and round the result to two decimal places. 3.40 3.50 8.75 2.18