#### Answer

The percentage of change in the number of phones sold between May and June is +24%, so it is a percent increase.

#### Work Step by Step

The cell phone store sold 200 phones in May and 248 phones in June.
To find the percentage of change, we use the following formula:
Percent of change = $\frac{New\ amount\ -\ Original\ amount}{Original\ amount}$ $\times$ 100%
The new amount is 248, and the original amount is 200.
We substitute these values into the equation to obtain:
Percentage change = $\frac{248 - 200}{200}$ $\times$ 100%
Percentage change = $\frac{48}{200}$ $\times$ 100%
Percentage change = 0.24 $\times$ 100%
Percentage change = 24%