Answer:
a = 20
Step-by-step explanation:
The mean is calculated as
mean = 
=
= 
Then
= 27 ( multiply both sides by 5 to clear the fraction )
115 + a = 135 ( subtract 115 from both sides )
a = 20
Answer:

Step-by-step explanation:
Given

i.e. first to fifth
Required
Determine number of selection
1st position = Any of the 30 students
2nd position = Any of the 29 students
3rd position = Any of the 28 students
4th position = Any of the 27 students
5th position = Any of the 26 students
Number of selection is then calculated as:


Answer:
y=4, x=8
Step-by-step explanation:
system:
x+y = 12, x=2y
convert to 1 variable, simplify:
2y+y=12
3y=12
y=4
x=2y=4*2=8
Answer:
A = 9x² + 12x
Step-by-step explanation:
The area (A) of the rectangle is calculated as
A = height × width
= 3(3x² + 4x) ← distribute parenthesis by 3
= 9x² + 12x
Answer:
x = 11
Step-by-step explanation:
A segment parallel to a side of a triangle cuts off proportional segments on the sides.
48/6 = (3x + 7)/5
8 = (3x + 7)/5
3x + 7 = 40
3x = 33
x = 11