Are you sure your in high school, also it's answer #3.
Answer:
24.75
Step-by-step explanation:
keychain=$6.75
t.shirt=X
according to question
X+6.75=31.50
X=24.75
Try adding 11, 11 times. It is a long process, but it should give you what you are looking for. First. to break it down add 10 eleven time, then after you get 110 add the remaining 11.
Answer:
22 grams
Step-by-step explanation:
loses 50% of it's mass per 22 years
so after 22 years the mass would be 44 grams
22 years later would leave 50% of 44 grams = 22 grams