80x20=1600 costumes
12x90=1080 masks
1600-1080=520
they ordered 520 more costumes than masks. hope this helps!
Answer:
A and B
Step-by-step explanation:
we would like to solve the following equation:

to do so isolate -x to the left hand side and change its sign:

simplify addition:

square both sides:

simplify square of the right hand side:

use (a-b)²=a²-2ab+b² to expand the left hand side:

swap the equation:

isolate the right hand side expression to the left hand side and change every sign:

simplify:

rewrite the middle term as 13x-2x:

factor out x:

factor out -2:

group:

by <em>Zero</em><em> </em><em>product</em><em> </em><em>property</em> we obtain:

solve for x:

to check for extraneous solutions we can define the domain of equation recall that a square root of a function is always greater than or equal to 0 therefore

solve the inequality for x:

since 2 and -13 is less than 5 both solutions are valid for x hence,

and we're done!
Answer:
w = 10
Step-by-step explanation:
First we take the two values for the breadth of the rectangle
So:
5x - 9 = 3x + 7
now we solve this equation as follows:
5x - 3x = 9 + 7
2x = 16
x = 8
now that we have found the value for x, we can substitute it in the equation, 5x - 9,or in the equation, 3x + 7.
when we substitute x in any of these equations, we get
5(8) - 9 = 31
3(8) + 7 = 31
now that we have the value for the breadth we can form the following equation:
31 × w = 310
31w = 310
w = 310/31 = 10
Answer:

Step-by-step explanation:
Multiply the quotient
by the divisor
for the dividend, that is
× 
Cancel the 3 on the numerator/ denominator
=
×
=
= 