Solve each system by substitution

7x-y=-6
4x+y=-5

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?

Arectangle has a width of 5 cm and a length of 10 cm. if the width is increased by 3, how does the perimeter change?

During a wright loss challenge your friend goes from 125 pounds to 100 pounds.what was the percent weight loss