Step 1- Find each element's molar mass:
K=39.1, Cr=52, O=16
Step 2-Multiply by their subscripts:
K=39.1*2=78.2
Cr=52*1=52
O=16*4=64
Step 3-Find the molecule's molar mass:
78.2+52+64= 194.2
Step 4- Divide each element's mass by the molecule's:
K: 78.2/194.2= 40.3%
Cr: 52/194.2=26.8%
O: 64/194.2=32.9%
(if this helped, can I get Brainliest? Competing against a friend. Thanks!)