Of the 20 students of the field trip, 12 are boys. what percent of the total number of students are boys

you get that percentage as a ratio of boys to total (times 100). So,

12/20 = 0.6

to get percentage, multiply by 100: 0.6*100 = 60%

60% of the students are boys

(sin 42)/31. = sinx)/37

sinx = 37 (sin42)/31

= 37× 0.66/31 = 0.787

x= 51.9

other angle opposite to y = 180-51.9-42

= 180- 93.9 =86.1

so

sin42)/31 = sin 86.1)/y

0.021 = 0.997 /y

y= 0.997/0.021 =47.47