Solve the following systems of equations without graphing 5x + 10y = 30

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

What term makes it inconsistent y=2x - 4

Which graph has figures that can undergo a similarity transformation to justify that they are similar? (obviously not the third one)