Ответ:\((15+50):5=65:5=13\).\((900-828):9=72:9=8\).\(48:8+36:12=6+3=9\).\(18\cdot5-5\cdot6=90-30=60\).Ответ: 1) 13; 2) 8; 3) 9; 4) 60.