Problem Solving

hello everyone,

i have a huge problem with calculation and i cant believe that we cant use calculator in the exam, my calculation problem is really keeping me from solving the problems right,i know the steps and everything but the calculation part is a great obstacle, i learned long division and long multiplication but it takes a long time to solve, that if i didn't make an error in the middle of all these numbers, and when i tried cancel the common factors and all these steps, the problem is that i cant recognize the common factor to cancel it, i don't see them especially in long numbers, all my life i use calculator for everything, please tell me how i can practice?? or where to find problems to practice on??? if there is some kind of book or website that can help,to get over this issue...

thanks, and good luck for you all...