(Image credit: Tom's Guide) You're at dinner, the bill arrives, and someone inevitably says: "so what do we each owe?" Cue the awkward phone shuffling — someone opens the calculator, someone else does it on the notes app, your friend is just guessing. It's a whole thing. But what if you never had to leave your keyboard? Since iOS 18, your iPhone has had this quietly powerful feature built right into the keyboard, meaning you no longer have to switch between apps for calculations. It works anywhere you type, and almost nobody knows it's there. Here's how to use it. Do math without leaving your keyboard Open any app where you type and type a math equation followed by an equals sign . For instance, type "25 + 17 =" and the answer "42" appears as a suggestion above your keyboard. Press the spacebar or tap the suggestion to insert the result . Your equation disappears, replaced by just the answer. This works for addition, subtraction, multiplication, and division.…