Ella simplifies (3 b + 4 r) + (negative 2 b minus r) and says the result is b Plus 5r. What error did Ella make?

Select the correct answer from each drop-down menu. a system of equations and its solution are given below. system a complete the sentences to explain what steps were followed to obtain the system of equations below. system b to get system b, the equation in system a was replaced by the sum of that equation and times the equation. the solution to system b the same as the solution to system a.]