Marco has $1.31 in his coin bank. He spends 87c to buy a pen. After he buys the pen, How much does he has left?

C. i believe it is (5×(-20))+(100×(0.7))

Ifound this on google “that means that the graph of a function with direct variation has these features: it is a straight line: because the slope is the ratio y/x = k. it passes through the origin (0,0): because y = kx = k (0) = 0.” i hope this you for what your looking for