math
posted by reena .
Bill buys x items at $3 each, y items at $5 each, and z items at 6 each. If x,y,and z are each multiple of 5 and the total price of the items costing $3 and $5 is 55, which of the following could be the total price of all x +y+z items?

3x + 5y = 55
the condition that must be satisfied is that x, y and z must all be multiples of 5.
first, we guess value of x (which must be a multiple of 5). And then we solve for corresponding value of y. Note that the value of y calculated must also be a multiply of 5. If it's not, guess another x value:
x: 5 , 10 , 15
y: 8 , 5 , 2
we see here that the only x and y value that satisfies the condition is
x = 10 and y = 5
now i think you forgot to type the choices.