What is the value of the expression below when n = 2.1?
An X 2 + 13

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

Can someone me and do the problem plz so i can understand it more better

Iwill give ! if m∠a=59 and m∠3=81°, what is m∠b? m∠b= _[blank]_°