Răspuns :
81-3x7-5x3+9x5= 81-21-15+45=60-15+45=45+45=90
18+3x(6x4-5x4)+4(8x4-6x5)=18+3x(24-20)+4x(32-30)=18+3x4+4x2=18+12+8=30+2=32
18+3x(6x4-5x4)+4(8x4-6x5)=18+3x(24-20)+4x(32-30)=18+3x4+4x2=18+12+8=30+2=32