Create a function that takes an input (e.g. "5 + 4") and returns true if it's a mathematical expression or false if not.
"5 + 4"
true
false
math_expr?("4 + 5") ➞ true math_expr?("4*6") ➞ true math_expr?("4*no") ➞ false
+, -, *, /, %