In the morning, Mr Wong took $$\frac{3}{4}$$ h to drive his car from his home to the airport.<br>In the afternoon, he took $$\frac{1}{2}$$ h to drive his car from the airport back to his home.<br>The airport was 45 km from his home. <hr> Find his average speed for his trips.<br> <input min="0" type="number" id ="imp6pg159q7b_1" class="lineinput" placeholder="?" /> $$km/h$$