MUST SHOW WORK NEED HELP!1 ASAP

Work Shown:

x/21 = 12/15 ... see note below

15x = 21*12 ... cross multiply

15x = 252

x = 252/15 divide both sides by 15

x = 16.8

Note: x is opposite the double arc marking and 21 is opposite the single arc marking. Similarly, 12 is opposite the double arc and 15 is opposite the single arc. This order is important to set up the proportion.

answer is because 4×10=40

and 98×4= is 392

40,392