I don’t understand help

a)-4x+7=9×3

-4x=27-7

x=-20/4

x=-5

b)49r-55r=-52+10

-6r=-42

r=-42/6

r=7

c)-6m+8m-2m=-1-5+6

2m-2m=0

0=0

1260=3*6*7*10=3^2*2^2*7*5 perfect cude = 3^3*2^

step-by-step explanation:

in counting the number of heads in 4 coin flips, the probability that we get exactly one head is the probability that we get anyone of the following 4 outcomes: httt, thtt, ttht, or ttth. each has probability 1/16, so the probability to get exactly one head in 4 flips is 1/16 + 1/16 + 1/16 + 1/16 = 4/16 = 1/4.