4辆大卡车运沙土，7趟共运走沙土336吨．现有沙土420吨，增加了3辆相同的卡车，问：几趟可以运完？3x(Y,@4B-T6W+B:C8j2}/d+o6i*d9n.x
算式：提示5R(b3g:f+}+G*c3r0b7N3x(Y,@4B-T6W+B:C8j2}/d+o6i*d9n.x
答：需要(i:^5|7N*v8c5R(Q-e4h0@+G/N,g(B趟就可以运完。3x(Y,@4B-T6W+B:C8j2}/d+o6i*d9n.x