Given:
Either has a school certificate or diploma or even both = 20 people
Having school certificates = 14
Having diplomas = 11
To find:
The number of people who have a school certificate only.
Solution:
Let A be the set of people who have school certificates and B be the set of people who have diplomas.
According to the given information, we have
We know that,
Subtract both sides by 25.
We need to find the number of people who have a school certificate only, i.e. 
.
Therefore, 9 people have a school certificate only.
2/7 + 4/7 = 6/7 Can be rewritten as
4/7 + 2/7 = 6/7
Answer: price of soda (a) = $2 and price of popcorn (b) = $0.5
Step-by-step explanation:
Let's denote soda = a and popcorn = b
Kaylin bought a soda and two popcorn, writing out an equation for this would be
a + 2b = $3...........equation (i)
And her brother bought 3 sodas and 1 popcorn.
3a + b = $6.50..........equation (ii)
From equation (i),
a + 2b = 3
Making a the subject of formula,
a = 3 - 2b......equation (iii)
Using substitution reaction, put equation (iii) into equation (ii)
3(3 - 2b) + b = $6.50
9 - 6b + b = 6.50
9 - 5b = 6.50
Collecting like terms,
5b = 9 - 6.50
Divide both sides by 5,
b = 5.
Put b = 5 into equation (i)
a + 2(0.5) = 3
a + 1 = 3
a = 2
Therefore, the price of soda is $2 per one and $0.5 for each popcorn.
