Răspuns :
notam caiete=a si creioane=b
40a+70b=108⇒a=108-70b/40
30a+18b=53,4⇒30(108-70b/40)+18b=53,4
(3240-2100b(/40+18b=53,4
3240-2100b+720b=2136
3240-1380b=2136
3240-2136=1380b
1104=1380b
b=1104:1380
b=0,8
a=108-70*0,8/40=108-56/40=52/40=1,3
caietul costa 1,3
creionul=0,8
40a+70b=108⇒a=108-70b/40
30a+18b=53,4⇒30(108-70b/40)+18b=53,4
(3240-2100b(/40+18b=53,4
3240-2100b+720b=2136
3240-1380b=2136
3240-2136=1380b
1104=1380b
b=1104:1380
b=0,8
a=108-70*0,8/40=108-56/40=52/40=1,3
caietul costa 1,3
creionul=0,8