a) This problem is transformation of the independent variable. The transformation consists of a shift and time scaling. The resulting signal is shifted to the left by 5 and time scaled so the new times are divided by 2.
b) This problem is finding the even and odd parts of a signal x[n]. x1[n] = (x[n] + x[-n])/2 is the even signal.
x2[n] = (x[n]-x[-n])/2 is the odd signal.
