laps in total workout = x
workout left = 0.35 or 35%
laps swum so far = 26
If kate has 35% of her workout left, that means she has already done 65% of her workout. (100% - 35% = 65%)
She has swum 26 laps so far, meaning 65% of her total workout is 26 laps.
0.65x = 26
divide both sides by 0.65
x = 40
there are 40 laps in her total workout