Let
be the random variable for the number of marks a given student receives on the exam.
10% of students obtain more than 75 marks, so

where
follows a standard normal distribution. The critical value for an upper-tail probability of 10% is

where
denotes the CDF of
, and
denotes the inverse CDF. We have

Similarly, because 20% of students obtain less than 40 marks, we have

so that

Then
are such that


and we find

Answer:
20x^2+23x+6
Step-by-step explanation:
(4x+3)(5x+2)
(4x)(5x)+2(4x)+(5x)3+3(2)
20x^2+8x+15x+6
20x^2+23x+6
Hope that helps :)
For 2/5 cup, vanilla needed = 8 teaspoons
so, for 1 cup, it would be: 8 / 2/5
⇒8 × 5/2
⇒40/2
⇒20
In short, Your Answer would be 20 teaspoons
Hope this helps!