Cos s = -8/17 and cos t = -3/5, s and t in quadrant 3

The depth of a lake at a certain point, wich is a function of the distance of that point from shore, is 30 feet.

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

If x is 6, then 7x= a. 13 b. 42 c. 42x d. 76