PLS SOMEONE HELP ME 3 7. The number of diagonals in a polygon with x sides is given by the formula: D = 1/2x^2 - 3/2x
Use the formula to determine the number of diagonals in a polygon with 12 sides.
Show all of your work.

The ivring berlin learning center would like a possible net profit of $650,000 on its new resource manual it sells to schools. the fixed costs for producing the manual are $780,000 and the variable cost per package is $19.85. if the estimated unit sales are 1,250,000 units, what selling price unit should the ivring berlin learning center try?

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?

Angie has saved 3/8 of the amount she needs to buy a bike. clive has saved 7/10 of the amount he needs to buy a skateboard. what is the difference between clive's and angie's fraction of savings?