Karla is given the equation 10x + 15 = 20 to solve. she says the solution is 1 2 . which reason justifies her solution? a) karla says that to solve the equation you first add 15 and then multiply by 10. b) karla says that to solve the equation you first multiply by 10 and then add 15. c) karla says that to solve the equation you first subtract 15 and then divide by 10. d) karla says that to solve the equation you first divide by 10 and then subtract 15.