It's baseball time!

If $x$ is the cost of the baseball and $y$ is the cost of the baseball glove, we can write:

$\large \begin{cases} x + y & = 1540~~~~~~ .....(1) \\ x - y & = -440 ~~~~~~ .....(2) \\ \end{cases}$

after $(1) + (2),$ we get,

$\begin{aligned} x + x & = 1540 + (-440) \\ 2x & = 1540 - 440 \\x & = \dfrac{1100}2 \\ x & = \boxed{550}. \\ \end{aligned}$

let b = cost of baseball and g = cost of baseball glove, then we have the two equations

b + g = 1540 (eq. 1)

b = g - 440 (eq. 2)

from (eq. 2), we get

g = b + 440

substitute the above in (eq. 1), we have

b + b + 440 = 1540

2b = 1100

b = 550 (answer)