It appears you have vertical angles. The rule with angles is that no matter what, vertical angles are always congruent (or the same). This means you would have to set up the equation to solve for "b" as:
70 - 2b = 28 + 5b
You could solve this manually, but Desmos graphing calculator is faster. Simply type this in and replace b with x and it will give you the answer, which is 6. Hope this helps!