Question

The daltons completed 30% of their 2140-mile trip the first day

Answer 1

$30\%\cdot2140=0.3\cdot2140=\boxed{642\text{ miles}}\\ 2140-642=\boxed{1498\text{ miles}}$

Answer 2

To figure out how many miles the Daltons traveled the first day you times 2140 miles and 30 percent.
So 2140 x .30 = 642
They traveled 642 miles the first day.

To figure out how many miles they still have to travel you subtract your original miles (2140) from how many miles they have already traveled (642).
So 2140 - 642 = 1498
They have 1498 miles to still travel.