Two adjacent sides of a parallelogram …

Take longer sides as base of parallelogram, which is equal to 24 cm. 

And, distance between longer sides as height (h), which is equal to 12 cm.

We know that, Area of Parallelogram = Base × Height 

                                                      = 24 × 12 

                                                      = 288 cm²

Now, take shorter sides as base of parallelogram, which is equal to 18 cm. 

Let, height = distance between shorter sides =$x$ cm

Since, area of parallelogram in both cases will be equal.

Therefore, Area of Parallelogram = 288 cm²

                           Base × Height = 288

                              18   ×  $x$     = 288

                                      $x$ = $\frac{288}{18} = 16$

Therefore, distance between the shorter sides is 16 cm. 

Given : Shorter Side = 18 cm

Longer Side = 24 cm

Distance b/w longer sides = 12 cm

Area of parallelogram = Side * Distance b/w

=> 24*12 = 288 cm²

Similarly in case of shorter side,

Area of parallelogram = Side * distance b/w sides

=> 288 = 18*distance b/w sides

=> distance b/w shorter sides = 288/18= 16cm