Create a function that takes a first-degree equation as a string and solves it. If there would be more than one solution, the function must return "Infinite solutions".
solver("2*x + 1 = x") ➞ -1.0
solver("7*x + x - 4 = 0") ➞ 0.5
solver("x = x") ➞ "Infinite solutions"
The given variable is always "x".