You can put this solution on YOUR website! If the point (2,7) is on the straight line whose equation is ax+by=20, form the linear equation.
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Pick any value for a and you can colve for b.
--> an infinite # of lines.
eg,
a = 1
x + by = 20
2 + 7b = 20
b = 18/7
x + 18y/7 = 20
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a = 2
2x + by = 20
4 + 7b = 20
b = 16/7
2x + 16y/7 = 20
etc