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{450-[1550-10X(a-12)]:4}:5=15

Răspuns :

Se duce 5 in partea cealalta inmultindu l pe 15; 450-[ 1550-10x(a-12)]:4= 15x 5= 75; se duce 450 ;,-[1550-10( a-12)]:4= 75-450= -375; se duce 4 inpartea dreapta ; 1550-10(a-12)= 1500; -10a+ 120= 1500-1500= 0; -10a= -120;,a= 12