Number 16 find the distance between the two points

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

Use circumcenter theorem to solve for the given values

What is a correct first step in solving the inequality-4(3-5x)> -6x+9