1+3=4
A counterexample is an a example that proves the statement false.
1+3 are not even numbers but they equal an even one, so it just proved the statement wrong.
Answer:
10
Step-by-step explanation:
first you need to find the prime factors of the three numbers
ex:
prime factor of 18= 
prime of 24=
there is one 2 and one 3 in common
greatest common multiple 2*3=6
so the greatest common multiple is ten because it is the only one that can divide between all three evenly.

so 10 is your answer
Answer:
9000 ft
Step-by-step explanation:
Given: A airplane is ascending at a constant rate of 15 feet per second,
What we need to know: The change in altitude during 10 minutes of flight,
60 seconds = 1 minute
60 × 10
= 600 seconds
600 × 15
= 9000 ft
Therefore there was a 9000 ft change in altitude during the 10 minutes of the flight.
1 = 1/4(2x+8)
1 = 1/2x + 2
1 - 2 = 1/2x
(-1) = 1/2x
x = (-1) : 1/2 = (-1) × 2/1 = (-2)
Answer : x = (-2)