#Lets just write x as the nunber you asked
x × 40/100 = 18
x = 18 : 40/100
x = 18 × 100/40
y = 1800/40
y = 45
<h3>
Answer : 45</h3>
Notice that half of the coefficient of x is (1/2)(-4), or -2.
Then x^2 - 4x becomes
x^2 - 4x + 4 - 4 = 0, or (x -2)^2 = 4. Then x = -2 plus or minus 2, and the two roots are 0 and -4.
Thus, add 4 to both sides to obtain x^2 - 4x + 4 = 4.
Answer:

The slope can be founded with this formula:

And replacing we got:

And the best answer for this case would be :

Step-by-step explanation:
For this case we have the following two points given:

The slope can be founded with this formula:

And replacing we got:

And the best answer for this case would be :

The probability is 4:20
It is correct because there are 20 students and there could be 4 guesses