Fill in the Blanks with + or - to Solve Equations

Insert the missing operation signs “+” or “–” to make the following equations correct:
a) $5 \, \_ \, 4 \, \_ \, 3 \, \_ \, 2 \, \_ \, 1 = 3$
b) $5 \, \_ \, 4 \, \_ \, 3 \, \_ \, 2 \, \_ \, 1 = 5$