Help me find x & y please

What's the difference between: x≥0 and nonnegative integer. ?

Ke’ajah has a coupon for 1/3 off the regular price, t, of a tent. which expression represents the price of the tent using the coupon? select the two correct expressions. a. 1/3t b. 2/3t c. t - 1/3 d. t - 2/3 e. t - 1/3t f. t - 2/3t

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?