If a polygon has four sides, then it is a quadrilateral.
If a polygon is a quadrilateral, then, it has four sides.
If I eat a pint of ice cream then I will gain weight.
If I gain weight then I ate a pint of ice cream.
If you add 5 and and 10, then you get a sum of 15.
If you got a sum of 15, then you added 5 and 10.
If you have a coupon, then you will receive a free drink with your pizza.
If you received a free drink with your pizza then you have a coupon.
"If Cliff is thirsty, then she drinks water."
" If Cliff drinks water then he is thirsty"
If two angles are congruent, then they have the same measure.
If two angles have the same measure, then they are congruent.
"If it rains, then they cancel school"
"If they cancel school, then it rains."
If you are a vegan, then you do not eat meat.
If you do not eat meat, then you are a vegan.