The answer to this is y=13
Answer:
93 square metres
Step-by-step explanation
The formula for surface area is 2ab+2ac+2bc, and with no lid one bc can be removed.
Suppose a=7 b=3 and c=3
2(7x3)+2(7x3)+(3x3)=93
To get the area of a square, You just square one side or multiply 2 sides, I'm not sure what the rounding is, but 6.25 times 6.25 is 39.0625