Solution:
we have given the length of the rectangular card-

and, width-

now, the area of the card will be- length×width.
so, we have-

we also have given the length of ribbon-

and, width-

so, area of the ribbon is-
length×width

now the area of shaded gray region will be-

Hence, the required expression would the above expression.
Diagonal of the rectangular prism=√(l²+w²+h²)
√(l²+w²+h²)=√(100+25+64)=√189 cm
I think is C tbh sorry if that’s wrong my fault
Answer:
x = 3 +- √18
Step-by-step explanation:
By completing the square method