Question 509700
{{{ 15a-2(4a+5)=-6a }}}
{{{ 15a - 8a - 10 = -6a }}}
Add {{{6a}}} to both sides
{{{ 15a - 8a + 6a - 10 = 0 }}}
Add {{{10}}} to both sides
{{{ 15a - 8a + 6a = 10 }}}
Do the indicated addition and 
subtraction of terms on the left side
{{{ 13a = 10 }}}
{{{ a = 10/13 }}}
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You can check this by putting 
answer back into original equation
I'll use decimal equivilant {{{ 10/13 = .7692 }}}
{{{ 15a-2(4a+5)=-6a }}}
{{{ 15*.7692-2(4*.7692+5)=-6*.7692 }}}
{{{ 11.5385 - 2*(3.0768 + 5) = -4.6152 }}}
{{{ 11.5385 - 2*8.0768 = -4.6152 }}}
{{{ 11.5385 - 16.1536 = -4.6152 }}}
{{{ -4.6151 = -4.6152 }}}
OK- the error must be due to rounding off