Given the system of equations presented here: 3x + 5y = 29 x + 4y = 16 which of the following actions creates an equivalent system such that, when combined with the other equation, one of the variables is eliminated? a) multiply the second equation by −1 to get −x − 4y = −16 b) multiply the second equation by −3 to get −3x − 12y = −48 c) multiply the first equation by −1 to get −3x − 5y = −29 d) multiply the first equation by −3 to get −9x − 15y = −87