Suppose y varies inversely as x. if x = - 13 and y = 100, find y when x = 5

The equation for an inverse or indirect variation is y = k/x. Fill in those value to first solve for k: 100=k/-13. Multiply both sides by - 13 to get that k = - 1300. Now use that k and the x value of 5 to solve for y: y = - 1300/5. Divide that out to get that y = - 260