find the current Is?

In the circuit, the terminals of R₃ is short circuited. Hence, no current passes through R₃.
To make it simple, R₃ is removed as shown in the figure below.

R₁ and R₂ are in parallel.
Equivalent resistance of R₁ and R₂, R
= 1 / [(1/R₁) + (1/R₂)]
= 1 / [(1/9) + (1/5)] Ω
= 3.2 Ω

V = Iₛ × R
Hence, Iₛ
= V/R
= 5/3.2 A
= 1.6 A