The smallest prime number is 2. So the numbers can be __2. Now for the tens digit, it can be 3,4,and 5 giving 3 possibilities. And finally, the hundreds digit can be 8 or 9.
So there are 6 numbers that satisfy these conditions.
Btw, if you want to double check, the numbers are 832, 842, 852, 932, 942, and 952.
Based on looking at other problems similar to this, I think you meant 1/3 of the total load which means if we say t=800+x and t=4/3x then subtract the first equation from the second, we get 1/3x=800, or x=2400. Then to solve for t we add 800 to get t=3200.
So the greatest load the truck can carry is 3200 pounds.
Well, we can say it is (x+y)^2 which expanded is x^2+2xy+y^2. We can see in the original equation it is x^2 which is in our expanded equation and then 8x is 2xy in the expanded equation. This means that 2xy=8x, or y=4. This means the blank which is y^2 is 4^2 or 16.
So the constant is 16 and the equation is x^2+8x+16.