You need to know conversion factors in Customary system: 1ft=12in, 1yd=3ft, 1gal=4qt, etc.
5yd 2ft 10 in + 3yd 1ft + 4yd 2ft 9 in=12yd 5ft 19in. As you know 12in=1ft, then 19in=1ft 7in, 5ft+1ft 7in= 6ft 7in, and 6ft=2yd, so the answer is 14yd 7in.
Multiply 6ft 5 in by 4= 24ft 20in=25ft 8in=8yd 1ft 8in
and so on.