Answer:
A. 
B. 
Step-by-step explanation:
Consider the equation

A. This equation has no solutions when the coefficients at x are the same and the free coefficients are not the same.
First, use distributive property:

So, the equation is

This equation has no solutions when

B. The equation has infinitely many solutions when the coefficients at x are the same and the free coefficients are the same too.
So, the equation

has infinitely many solutions when

In other cases, the equation has a unique solution
Let's say X is the first brother's age
x+2 is second brother, and x+4 is the third brother
Since the product of the first and third boy x(x+4) is 20 more than twice (20+x(x+2), our equation is x(x+4)=20+2(x+2)
Simplify from there and see what you get.
Answer:
90/1.5=60 mph
Step-by-step explanation:
I assume that the train is traveling at constant speed.
Between 12:45 pm and 2:15 pm the train has traveled 180-90=90 miles. So 90 miles in 1.5 hours which means that its speed is 90/1.5=60 mph
The correct solution is 75.
Step-by-step explanation:
surface area = (2*0.5*12*8) + (2*10*10) + (12*10)
= 96 + 200 + 120
= 416 cm^2