2 is the unknown number.
Let x be the unknown number.
2x + 19 = 23
2x = 23 - 19
2x = 4
2x/2 = 4/2
x = 2
to check:
2(2) + 19 = 23
4 + 19 = 23
23 = 23
So you would substitute 3 in for A
2(a)=2(3)=6
x=6
Infinity raised to any number greater than 1 is always equal to infinity. But if infinity is raised to 0, then the result is indeterminate. Normally, if any number is raised to 0 is 1 but it is different for infinity.