Bob has a bag full of dimes and quarters. He has 20 coins worth $3.80. Which system of
equations could be used to determine the
number of dimes, d, and the number of
quarters, q, in Bob's bag?

x+y=20

.10x+.25y=3.80

Step-by-step explanation:

A) sin 120=sin (180-60)=sin 60= (It lies on second quadrant where sin is +ve)
B)  tan (150)=tan(180-30)=-tan30=(It lies on second quadrant where tan is -ve)
C) cos (-135)=cos (135)=cos (180-45)=-cos (45)=(It lies on second quadrant where cos is -ve)
D) sec (300)=sec (360-60)=sec(60)=2 (It lies on fourth quadrant where sec is +ve)
E) sin (240)=sin(180-(-60))=sin(-60)=-sin (60)=
(It lies on third quadrant where sin is -ve)
 F) cos (330)=cos(360-30)=cos(30)=
(It lies on fourth quadrant where cos is +ve)
sin (240)- cos (330)=