Question 650938
{{{(9k+30)-(4k+10)=100}}} first remove the parentheses,

recall:

When parentheses are preceded by a plus sign + simply remove them.  Nothing changes.

When parentheses are preceded by a minus sign−change the sign of every term within the parentheses.

{{{9k+30-4k-10=100}}}


{{{9k-4k+30-10=100}}}


{{{13k+20=100}}}


{{{13k=100-20}}}


{{{13k=80}}}


{{{k=80/13}}}


{{{k=6.1538461538461538461538461538462}}}....round


{{{k=6.15}}}