x3 := 2
y3 := 17
h := 2

fExp[x_] := A*e^(B*x)

Solve[fExp[0] == h, A]
{{A -> 2}}

A := 2

Solve[fExp[x3] == y3, B] // N
{{B -> ConditionalExpression[0.5 (2.14007 + (0. + 6.28319 I) C[1]), C[1] \[Element] Integers]}}

B := ¿?