If there is 23 classrooms and each has 10 then you would have to times 23 by 10 - 23x10=230
4, 7 and 9 are mutually coprime, so you can use the Chinese remainder theorem.
Start with

Taken mod 4, the last two terms vanish and we're left with

We have
, so we can multiply the first term by 3 to guarantee that we end up with 1 mod 4.

Taken mod 7, the first and last terms vanish and we're left with

which is what we want, so no adjustments needed here.

Taken mod 9, the first two terms vanish and we're left with

so we don't need to make any adjustments here, and we end up with
.
By the Chinese remainder theorem, we find that any
such that

is a solution to this system, i.e.
for any integer
, the smallest and positive of which is 149.
Surface area of the pyramid= 4*(area of the triangle) + area of the square
Area of the triangle = (1/2)*base*height=(1/2)*5*5= 25/2 in²
Area of the square = 5*5 =25 in²
Surface area of the pyramid = 4*(25/2) + 25=2*25 + 25=75 in²
Answer:
no a equilateral triangle has the same length sides all the way around