Hey can you me posted picture of question

What are “like terms”? why can we only add like terms?

Which of the statements about the graph of the function y = 2x are true? check all of the boxes that apply. the domain is all real numbers x because the exponent of 2 can be any real number when the x-values increases by 1 unit, the y-value multiplies by 2. the y-intercept is (0, 1). the graph never goes below the x-axis because powers of 2 are never negative. the range is all real numbers.

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15