remember
(a/b)(c/d)=(ac)/(bd)
just multiply tp and bottom
and
(-)(-)=(+)
(+)(+)=(+)
(+)(-)=(-)
(-)(+)=(-)
and distributive property
a(b+c)=ab+ac
so
-4/5(-15/16)=(-4*-15)/(5*16)=(60)/(80)=6/8=3/4
-3(x-4)-4(5x-1)=
-3(x)-3(-4)-4(5x)-4(-1)=
-3x+12-20x+4=
-3x-20x+12+4=
-23x+16
