Anyone know how to do this

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

Choose the number sentence that shows the identity property of addition. a. 122 = 61 + 61 b. 62 = 1 + 61 c. 61 = 0 + 61

Find the commission on a $590.00 sale if the commission is 15%.