Math Help..!? for smart people x]?

Question

i have 5 questions for u all involving math i have the answers but i want to know if I'm rite.. like double check lol..

1) a 12-foot tree casts a 16-foot shadow.How many feet tall is a nearby tree that casts a 20-foot shadow at the same time?

2) evaluate: 2x to the 2nd power + 5 wen x=3?

3)Julio's wages vary directly as the number of hours that he works. IF his wages for 5 hours are $29.75 how much will he earn for 30 hours?

4) seth bought a used car that had been driven 20,000 miles. after he owned the car for 2 years the total miledge of the car was 49,400 find the average number of miles he drove each month during those two years.

Answer 1

1. 15 ft

2. 23

3. 178.5 $

4. 1225  miles

Answer 2

1) use similar triangles (equal ratios)

12/16 = x/20 ; x = 15

2) 2x² + 5 = 2(3)² + 5 = 23

3)ratio again

5/29.75 = 30/x ; x = (30*29.75)/5 = 178.5

4)(49400 - 20000) = 29400 (additional mileage)

29400/24months = 1225miles per month

Answer 3

1)(12\16) = (x\20)

   x = 15

2)2x^2 + 5

  = 2x^2 + 5

when x=3,

2(3)^2 + 5

=23

3) $29.75\5h = $5.95\1h

  ($5.95\1h) x 30h = $178.50

4)(49,400-20000)/(2x12months) = 1225miles