Losing 30% of its value is the same as saying it is now worth 70% of its original value. To find 70% of 50,000 you can do 50,000 x 0.7. The answer will be the new value of the car after one year. After two years you are essentially finding 70% of the new value which is 70% of the original. More simply, it is 50,000 x 0.7 x 0.7. An equation for this (and the answer to 1b) is 50,000 x 0.7^t where t is the number of years.
1a (i) is $10500 (50,000 x 0.7^1)
(ii) is $2521.05 (50,000 x 0.7^5)
(iii) is $1412.38 (50,000 x 0.7^10)
1b 50,000x0.7^t