A museum humidifier contains 100 gallons of water. The system uses 10 1/4 gallons of water on​ Monday,
14 1/2 gallons on​ Tuesday,
7 7/8 gallons on​ Wednesday,
20 3/4 gallons on​ Thursday,
13 5/8 gallons on​ Friday,
10 1/2 gallons on​ Saturday, and
13 3/8 gallons on Sunday. Find the total number of gallons of water remaining.

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?