How many seconds are in a millenium? Standard form please

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

Find and simplify an expression for the area of five rows of x squares with side lengths of x centimeters.

Kathy spent 5/8 of her money on books and another 1/6 of her money on stationeries.what fraction of kathy’s money was left?