Hi Mike,

You can definitely use Solver in Excel to solve for two unknowns in a linear equation. Here's how you can do it:

1. First, enter your equations in Excel. In your example, you have two equations:
   x + y = 1
   3x + 4y = 7
   
2. Next, you need to set up Solver. Go to the "Data" tab in Excel and click on "Solver" (if you don't see Solver, you may need to install it first).
   
3. In the Solver Parameters dialog box, set the "Set Objective" field to the cell where you want to see the result. In this case, let's say you want to solve for x and y in cells A1 and B1, respectively. So you would set the "Set Objective" field to A1.
   
4. In the "By Changing Variable Cells" field, enter the cells that contain the variables you want to solve for. In this case, you want to solve for x and y, so you would enter A1:B1.
   
5. In the "Subject to the Constraints" section, you need to enter the constraints for your equations. For the first equation, you would enter:
   A1 + B1 = 1
   
   For the second equation, you would enter:
   3A1 + 4B1 = 7
   
6. Finally, click on "Solve" and Solver will find the values of x and y that satisfy both equations.

That's it! Solver will give you the values of x and y that satisfy both equations. If you have any other questions, feel free to ask.