Question 227584
Let {{{C}}} = total charge
{{{C = 12h + 20}}} (general equation)
And, if {{{C = 80}}}
{{{80 = 12h + 20}}} (specific case)
{{{12h = 80 - 20}}}
{{{12h = 60}}}
{{{h = 5}}} (hours to mend boiler)