ex 2 a) 73×538-73×500-73×37=73×(538-500-37)=73×1=73
b)3+6+9+... +90=(90+3)×88:2=93×44=4902
c)300×299+299×298-598×198=[299×(300+290)]-598×198=(299×598)-598×198=178802-598×198=178802-118404=60398
ex 4
(12×x+24)÷12-625÷125=1
(12×x+24)÷12-5=1
(11×x+24)=6×12
12×x+24=72
12×x=72-24
12×x=48
x=48÷12
x=4
sper ca te-am ajutat
cred ca merit coroana:)
