Evaluating Simple Algebra

Given a string containing an algebraic equation, calculate and return the value of x. You'll only be given equations for simple addition and subtraction.

Examples

eval_algebra("2 + x = 19") ➞ 17

eval_algebra("4 - x = 1") ➞ 3

eval_algebra("23 + 1 = x") ➞ 24

Notes

• There are spaces between every number and symbol in the string.
• x may be a negative number.