Monica's initial weight (before the diet) was 80 kilograms.
How to find the initial weight?
We know that after doing a diet, Monica lost 12% of her weight, which we can define as W.
After this weight lost, she has a final weight of 70.4kg
Then we can set up the equation:
W*(100% - 12%)/100% = 70.4kg
W*0.88 = 70.4kg
W = (70.4kg)/0.88
W = 80kg
That is her initial weight.