Which eaqution could be the result 3a+b=225 and b=a-15 in substiution

What number should be added to the expression x^2+3x+ in order to create a perfect square trinomial? 3/2 3 9/4 9

Interest begins accruing the date of the transaction except for auto loans mortgages credit card cash advances credit card purchases

You have 37 coins that are nickels, dimes, and pennies. the total value of the coins is $1.55. there are twice as many pennies as dimes. find the number of each type of coin in the bank.