If the cost of a bat and a baseball combined is $1.10 and the bat cost $1.00 more than the ball how

Let a be the cost of the ball and b be the cost of the bat:

We're given 2 equations:

1. a + b = 1.10
2. b = a + 1

Substitute equation (2) into equation (1) for b:
a + a + 1 = 1.10

Combine like terms:
2a + 1 = 1.10

Subtract 1 from each side:
2a + 1 - 1 = 1.10 - 1
2a = 0.10

Divide each side by 2:
2a/2 = 0.10/2
a = 0.05