Step 1: Understand what is asked
The question is what is Daphnie's orginal weight?
Step 2: Plan how to slove
I will use addition to find the original weight of Daphnie when she didn't loose 2.6 kg yet.
Step 3: Soluution
What will we add?: 81.5 kg and 2.6 kg
81.5 + 2.6= 84.1
Step 4: Check
If we minus 84.1 to 2.6 it is equal to 81.5
84.1 - 2.6= 81.5
Hope it helps