Answer:
First question
(A)
If As represent Sarah's age, B represents her sister's age, and C represents her brother's age, the expression we get for the relationship between their ages is A - 20 = B = C + 12
(B)
If her brother is 1, her sister is 13, and she is 33.
Second question
Equation: 101 = 9+4x
Answer: 23 art class students
Explanation:
First question
(A)
Let A represent Sarah's age, B represent her sister's age, and C represent her brother's age.
We are told Sarah is 20 yrs older than her sister: A - 20 = B
We are told Sarah's brother is 12 yrs younger than Sarah's sister: C +12 = B
Combining these two equations, we get: A - 20 = B = C + 12
(B)
If her brother is one year old, then C = 1.
B = C + 12 = 1 +12 =13
A - 20 = B, A = B+20=13+20=33
So if her brother is 1, her sister is 13, and she is 33.
Second question
We are told that the total number of students in the seventh grade is 9 more than 4 times as many students as there are in the art class. Write this out as an expression bit by bit to solve.
"4 times as many students as there are in the art class": 4X
"9 more than 4 times as many students as there are in the art class": 9 + 4X
"The total number of students in the seventh grade (101) is 9 more than 4 times as many students as there are in the art class": 101= 9 +4X
Solve this to fins the number of art class students:
101=9+4X
92=4x
x=23