Keyboard

I love Khan Academy, I just started using it the other day and I am in love, along with the IXL membership my mom got me, I am flying through for studying for this big exam I have in 3 weeks. They just gave me a list of what I had to learn, and we had to learn it on our own. But... it has some downsides, So I was on Khan Academy, and it said to rewrite a formula- which I was fine with, and the formula had Variables like c and stuff, and I had to type a bunch of variables as my answer, and the answering keyboard didn’t have any variables!! I couldn’t type my answer! Included is a pic. The only variable on the keyboard was C and I needed like H and I and Z... please fix, its rewriting formulas.