You could do this step by step or all in 1 statement. I will do it step by step because that's the way I would teach it.
i1
i1 = 4 * (1/2)^(1 - 1) Reduce the power
i1 = 4 * (1/2)^0 Change 1/2 to 1
i1 = 4 * 1 = Multiply 4
i2
i2 = 4 * (1/2)^(2- 1) Same directions as above
i2 = 4*(1/2)^1
i2 = 4*1/2 = 2
i3
i3 = 4 * (1/2)^(3 -1) Same directions as above.
i3 = 4 * (1/2)^2
i3 = 4 * 1/4
i3 = 1
Total 7
