So the one time payment is $15, and the one with variable is $0.25, so the equation is 15+0.25X=30.75 in order to find out how many minutes he used, first subtract 15 from both sides, now ur left with: 0.25X=15.75 now to isolate the variable, divide 0.25 from both sides, 0.25 divided by 0.25 cancel out leaving u with the variable. divide 15.75 by 0.25 X=63 So Matthew used 63 minutes.
