Shaman has 215 photos on his cell phone he deletes some so that only 129 photos remain what is the percent decrease in the number of photos

First find how many were deleted, by subtracting the remaining amount from the original amount:

215 - 129 = 86 pictures deleted.

Now divide the amount deleted by the original amount:

86 / 215 = 0.4

Multiply by 100:

0.4 x 100 = 40%

There was a 40% decrease.