What is the probability of rolling a prime number of a standard 20-sided die? (1 is not a prime number.)

a. 7/20

b. 2/5

c. 9/20

d. 1/2

  b.  2/5

Step-by-step explanation:

There are 8 prime numbers in the range 1–20, so the probability is ...

  8/20 = 2/5

47 - 90 = 43

43 - 180 = x

x = 137

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -