How to write equivalent expressions by combining like terms

Aparallel system functions whenever at least one of its components works. consider a parallel system of n components, and suppose each component works independently with probability 0.5. find the conditional probability that component n works given that the system is working

Simplify the expression 10/11(22z) + (a+5) -1

Given sin28.4=.4756, cos28.4=.8796, and tan28.4=.5407 find the cos of 61.6