How do you make the delta symbol using the keyboard? know, the triangle thing. i couldnt figure out where to put this question, so its going here

What is the volume of a cardboard box that measures 1 inch by 5 inches by 7 inches? the volume of the cardboard is cubic inches. enter your answer as the number that correctly fills in the blank in the previous sentence. if necessary, round your answer to the nearest tenth, like this: 42.5