Can't see how they get this answer [calc/prob]

Binomial distribution

I can not see how this is solved I am entering .5 for 1/2

(.5)¹(1-.5)³-¹ which the booklet says equals 3/8

But .5¹=.5 (1-.5)³-¹=.5² -----> .5(.25)= 1/8 this is what I get.