Question 209848
Let x = the amount earned last month, then x+$50 would be the amount earned this month.  The sum of these two amounts is $870.
x + (x+$50) = $870 Simplify.
2x+$50 = $870 Subtract $50 from both sides.
2x = $820 Divide both sides by 2.
x = $410 This is the amount earned last month.
$410+$50 = $460 This is the amount earned this month.