a) (x+450)-3450=4000:80

b) 15*(r-10)=255

c) d*(2632:56)=611

d) (1234+n)+2140=52741

(х+450)-3450=4000:80
(х+450)-3450=50
х+450=3450+50
х+450=3500
х=3500-450
х=3050

15·(r-10)=255
r-10=255:15
r-10=17
r=17+10
r=27

d·(2632:56)=611
d·47=611
d=611:47
d=13

(1234+n)+2140=52741
1234+n=52741-2140
1234+ n=50601
n=50601-1234
n=49367