What is the value of 15x - 20x?

A. -35x
B. -5x
C. 5x
D. 35x

Step-by-step explanation:

15x - 20x = -5x

answer is B

The answer is in the image 

The answer is in the image 

The solution is given in the image below

30% of 420 are first year students

first year students = (30/100 )*420

=126 students

Student who are not in first year = 420-126

=294 students  

Let the father's age be x and son's be y

10 years before-

Father age=x-10

sons age=y-10

Given,

x-10=10(y-10)

x-10=10y-100

Given present age of father=40

therefore,

x=40

40-10=10y-100

10y-100=30

10y=130

y=130/10

y=13

Therefore present age of son=13years

Given height of gymnasium is 5/6 height of 30 foot ball

therefore height of gymnasium=5/6 * 30

=25 feet

Cost before sale tax=$46.00

Cost after including tax=$48.76

Sale tax=$48.76-46.00

=$2.76

we know,

sale tax=((sales tax rate)/100) * cost before sale tax

2.76=((sales tax rate)/100) *46.00

sale tax rate=(2.76*100)/46

                   =276/46

                    =6%

There fore sales tax rate=6%

Total fabric purchased = 1 1/4 = 5/4

Fabric used = 3/4

Fabric left = 5/4 - 3/4

                 = 2/4

                 =1/2 yard

III is the case of joint variation as Area A depends on l and w

In I and II it depends on s and r respectively as pi is constant