Question 1128428


{{{80=10t+30(t-2)}}}
{{{80=10t+30t-60}}}
{{{40t=80+60}}}
{{{40t=140}}}
{{{t=140/40}}}
{{{t=3.5}}}

answer:{{{t=3.5h}}}

PROOF:

{{{80=10*3.5+30(3.5-2)}}}
{{{80=35+30*1.5}}}
{{{80=35+45}}}
{{{80=80}}}