Easy!
You take the total number of students (55) then you remove the people that only like math and remove the people that only like English and remove the people that like none of them and what’s left is how many like both subjects.
55-15-18-5=17 students that like both subjects!
Part A
Your problem statement already shows you the conversion.
Bottles purchased: 5×10¹⁰
Bottles recycled: 8.3×10⁹
Part B
The ratio of bottles purchased to bottles recycled is
... (5×10¹⁰)/(8.3×10⁹) = 0.6×10¹ = 6.0
The number of bottles purchased is 6 times the number of bottles recycle.
When I solved it I got 26648.8
to have 2.40$ between 30 dimes and nickels she would have to have 18 dimes being 1.80$ and 12 nickles being .60 cents.