(2*с+ а - 21)/(c/a*b+1)

include irvine32.inc
.data
a byte 1,0
c1 byte -1,0
d byte 255,0
chisl word ?
znamen word ?
result word ?
.code
main proc
;-------------------- знаменатель
mov eax,0
mov al, c1
idiv a1
mov al,a1
imul b1
add al,1
cbw
mov znamen,ax
;---------------------числитель
mov ax,2
imul c1
add al,a
sub al,21
cbw
mov chisl,ax

;--------------------- результат
cwd
idiv znamen
mov result,ax
exit
main endp
end main