First is yes
Second is no
Third is no
Fourth is no
Answer:
The sum of 1.8 and 1.56 is 3.36 according to the model
Sum of decimals
Given the expression 1.8 + 1.56
Using the partial sum method
1.8 + 1.56 = (1.0 + 0.8) + (1.0+0.56)
Regroup as whole and decimal number
1.8 + 1.56 = (1.0 + 1.0) + (0.8 +0.56)
1.8 + 1.56 = 2.0 + 1.36
1.8 + 1.56 = 3.36
Hence the sum of 1.8 and 1.56 is 3.36 according to the model
You can solve the problem this way:
Your money is increading $6 a week while sister's is decreasing $7 a week (because she isn't saving any and is spending $7 of what she has weekly)
Your money each additional week vs sister''s:
80/145 (Week 0)
86/138 (Week 1)
92/131 (Week 2)
98/124 (Week 3)
104/117 (Week 4)
110/110 (Week 5) The amounts are the same in 5 weeks.
and 
