Discrete Math 1: Please explain and prove each step with clear handwriting, and write every detail so that I can understand for future problems. This is discrete math one so please do not make it very complicated.

PLEASE MAKE THE HANDWRITING AND THE STEPS CLEAR AND ORGANIZED

PLEASE SOLVE both B AND C USING (n+(r-1) choose n) where n=40 and r-7.

Problem 2 (5 pts): How many solutions are there to the equation X1 + X2 + . . . + x7 = 40. (b, for 2 pts.): where the xi's are nonnegative integers and xi 3 3? (c, for 2 pts.): where the a,'s are nonnegative integers and , r5, r6, r7 are positive