Alex was thinking of a number. Alex doubles it, then adds 20 to get an answer of 22. 7. What was the original number?.

Ateacher brought a pack of 17 batteries . each calculator uses 3 batteries . how many calculator can the teacher fill with batteries

Which one is the correct answer, and why?

George writes the mixed number as sum and uses the distributive property 1/2.-2/5=1/2-2+2/5=1/2