# fill out the method below
# then test tho see if you did them correctly with
#  $ rake 1:1

# Given a number, return 20 less than, that number multiplied by 5
# 
# arithmetic1(10)     # => 30
# arithmeitc1(10.5)   # => 32.5
# arithmeitc1(-6)     # => -50

def arithmetic1(n)
  n * 5 -20
end
