Which function passes through the points (2, 15) and (3, 26)?

Assuming it's a linear function, you can solve this by doing the following; 
1.) Fine the slope - y2 - y1 / x2 - x1
                                26 - 15 / 3 - 2
                                     11 / 1
The slope is 11

2.) Standard form for a linear equation - y = mx+b
                                                                26 = 11(3) + b
                                                                26 = 33 + b
                                                                -7 = b

The final answer (in standard form) is y = 11x - 7

If you need it in any other form just comment and I'll help you out