Translate each sentence into an equation, then solve the equation the sum of 7,9, and a number is 40. find the number

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

Acollection of coins has value of 64 cents. there are two more nickels than dimes and three times as many pennies as dimes in this collection. how many of each kind of coin are in the collection?

For the feasibility region shown below find the maximum value of the function p=3x+2y