The operations should not follow normal order of operations. Who remembers PEMDAS

• P: Parentheses first
• E: Exponents (ie Powers and Square Roots, etc.)
• MD: Multiplication and Division (left-to-right)
• AS: Addition and Subtraction (left-to-right)

Instead, follow operations from left to right:

• "3+5*2-5" should be 11
• "3+100-50+2 should be 55
• "3*100-50/2" should be 125
• "1234567+5*2-5" should be 2469139