step 1. total production since 1953 = 53,807 cars ÷ 4% = 53,807 ÷ 0.04 = 1,345,175 cars
step 2. 1979 Corvettes with manual transmission = 53,807 x 23% = 53,807 x 0.23 = 12,375 cars
step 3. 1979 Corvettes with manual transmissions as a percentage of total production =
12,375 cars ÷ 1,345,175 cars x 100% = 0.92%