Looking at the equation: 25x+22y=488, I can see that y=4 and x=16 but how to I write the steps to solve this equation?
25(16) + 22 (4) = 488
400 + 88 = 488
If you mean "what steps do I use to show that (x,y)=(16,4) is an answer?", then the steps you showed are just fine. If you mean "what steps do I use to find this and other answers?", then you can see how to do that here. The equation is for a straight line and every answer for the equation is a point on the line. You can pick whatever numbers you want for one of the letters and then you solve for the other letter. Like:Looking at the equation: 25x+22y=488, I can see that y=4 and x=16 but how to I write the steps to solve this equation?