First find out how much the 4 volleyball nets are by using 4*28 which would equal to 112. Now subtract 112 from 250 and that leaves you with 138. Then you divide 138 by 7 which will give you about 19.7 which you need to take all decimals out since it isn’t an whole number. The gym teacher can only buy 19 volleyballs.
Answer:
b
Step-by-step explanation:
The Planck–Einstein relation

gives that E, the photon energy, is equal to h, Planck's constant, times <span>ν</span>, the frequency.
We can solve the equation in terms of frequency to get

We substitute our given energy,

, and Planck's constant,

.
It is the same thing as the average you add everything up then you divide by the number of numbers you added together