The school built a teaching building and transported a batch of steel materials, 15% of the total amount was used for the first time, 10 tons were used for the second time, and 1/5 of the total amount was used for the third time, leaving 55 tons of steel materials. How many tons does it weigh in total (use the equation to solve it)
学校修建教学楼运来一批钢材，第一次用去总数的15%，第二次用去10吨，第三次用去总数的(1/5)，还剩下55吨，这批钢材共重多少吨(用方程解答)
<result>100</result>