These apps have really helped me a lot with maths.
1) Photomath - it's like a calculator for any sums but it gives you step-by-step instructions on how to do it. It doesn't work with hand written problems or word problem.
2) Got it! - You send a picture of any problem (word or numerical) and a tutor will help you with it. It's basically like grinds but online!!
Both apps really helped me and they're free! I recommend you download them!