Anais bought 2 1/2 yards of ribbon. she had 2 feet 8 inches of ribbon left after trimming some curtains. how many inches of ribbon did anais use to trim the curtains?

You are given a length in yards, a length in feet and inches, and you need an answer in inches.
The first step is to convert yards into inches and the length in feet and inches also to inches.

1 yd = 36 inches

2 1/2 yd = 2 1/2 * 36 in.

2 1/2 yd = 90 in.

She bought 90 in. of ribbon.

1 ft = 24 in.

2 ft 8 in. = 2 * 12 in. + 8 in. = 24 in. + 8 in. = 32 in.

She had 32 in. left.

90 in. - 32 in. = 58 in.

She used 58 inches.