How to solve algebra equations in swift

Code Block 
func solve(a: Int, b: Int, c: Int) -> Double {	// solve ax + b = c
	if a == 0 {
		if b == c {
			print("Any x is a solution")
		} else {
			print("no solution")
		}
		return 0.0
	} else {
		return (Double(c - b)) / Double(a)
	}
}

Code Block 
func solve(_ a: Double, _ b: Double, _ c: Double) -> Double {		// solve ax + b = c
		if a == 0 {
				if b == c {
						print("Any x is a solution")
				} else {
						print("no solution")
				}
				return 0.0
		} else {
				return (Double(c - b)) / Double(a)
		}
}
func resolve(equation : String) -> Double {			 
		var equation = equation
		var aCoeff = 1.0
		var bCoeff = 0.0
		var cCoeff = 0.0
		
		if let xRange = equation.range(of: "x") {
				var aStr = equation
				aStr.removeSubrange(xRange.lowerBound..<equation.endIndex)			// remove everything after x
				aStr = aStr.replacingOccurrences(of: " ", with: "")
				
				if let a = Double(aStr) {
						aCoeff = a
				} else {		// No number just x or -x
						if equation.first == "-" {
								aCoeff = -1.0
						} else {
								aCoeff = 1.0		// Missing coeff, means 1 or -1
						}
				}
				equation.removeSubrange(equation.startIndex...xRange.lowerBound)			// keeps only after x (+ b = c)
		} else {				// if x missing, not an equation
				aCoeff = 0.0
		}
		
		if let equalRange = equation.range(of: "=") {
				var cStr = equation		 // The shorter, without x
				cStr.removeSubrange(equation.startIndex...equalRange.lowerBound)			// remove everything upto =, to keep only c
				cStr = cStr.replacingOccurrences(of: " ", with: "")
				if let c = Double(cStr) {
						cCoeff = c
				}
				// Remove after = and keep only "+ b"
				var bStr = equation
				bStr.removeSubrange(equalRange.lowerBound..<equation.endIndex)			// remove everything after =
				bStr = bStr.replacingOccurrences(of: " ", with: "")
				if let b = Double(bStr) {
						bCoeff = b
				}
				
		}
		
		return solve(aCoeff, bCoeff, cCoeff)
}
let equation = "- x + 5 = 3"
print("Resolve", equation)
let x = resolve(equation: equation)
print("x =", x)