XY=10
Y=X+3
X(X+3)=10
X^2+3X=10
X^2+3X-10
(X-2)(X+5)
Answer:
x = 12
Step-by-step explanation:
5x + 15 = 75
-15 -15
5x = 60
x = 12
Answer:
y = - 2
Step-by-step explanation:

The top 4 firms have (23 +22 +18 +12)% = 75% of the market.
The 4-firm concentration ratio is 0.75 or 75%.