Say that the two digit number you have is xy, which is really 10x+y (making it a two-digit number). Based from the first fact, you have the equation \(y+4=x\). The second fact gives you the equation \(3x+4y=47\). This is now a systems of equations. In order to make it a single-variable equation, multiple the \(y+4=x\) by 3, so it will now look like \(3y+12=3x\) and move around the variables to match the second equation. It will ultimately look like \(3x-3y=12\). Now subtract both equations from each other and you should be left with \(7y=35\). Divide both sides by 5 and you now know that \(y=5\). Plug the y-value that found back into the equation and solve. If \(y=5\), then \(x=9\). So the number was 95.
