[26×(6-2.5)÷0.5-25]×0.2 1993×20002000-2000×1993199379.31×0.6783×0.25+23.56+6.783×7.931×0.75-0.125×0.7931×67.83×8987×19861986-1986×19871987 6.8×0.32+0.32×4.2-8÷2528.67×67+3.2×286.7+573.4×0.050.25×4.5×6.4×1250