What is the answer for 7/10-1/2 in simplest form

When 142 is added to a number the result is 64 more times the number my options are 35 37 39 41

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog