Can somebody show me how to find a?

The isosceles triangle has two sides of equal length, a, that sre longer than the length of the base ,b. the equation 2a+b=15.7 can be used to find the sides length. if one of the longer sides is 6.3 centimeters what is the length of the base

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Sandy is ordering bread rolls for her party, she wants 3/5 of the rolls to be whole wheat. what other factions can represent part of the rolls that will be whole wheat? shade the models to show your work.