C=9 np if u need anymore I gotchu
<span>Using the information we have
3x+4=40
Do the same to each side of the equation to eliminate for x.
3x+4=40 Minus 4 from each side
3x=40-4
3x=36
Divide 3 from each side
x=36/3
x=12
AC=3x+4
insert the value of x
3(12)+4=40
AC=40
AD=20</span>
Answer:
Here c represents the total number of children in choir.
As per the statement:
Total number of boys in choir = 12
It is also given that: Three sevenths of a children's choir are boys.
⇒ Total number of boys = 
or

By cross multiply we have;
84 = 3c
Divide both sides by 3 we have;
c = 28
Therefore, the total number of children in choir is 28 children
3x+5y=10 and 5x-3y=-6 is perpendicular.
Radian: is the standard unit of angular measure, used in many areas of mathmatics.
degree: is a measuement of plane angle, defined by representing a full rotation as 360 degrees.
Both are two units for measuring angles. There are at least four such units, but degrees and radians are most likely to encounter high school and college.