x represents the cost of meals served in a week. The cost of meals or worth was $435, therefore, x = 435. 0.15 x 435= 65.25
Since she makes $56 along with 15% of meals served (which is $65.25), you add those together to get her final income the week she serves $435 worth of meals, so...
66.25+56=121.25
Unity makes $121.25 in a week that she serves $435 worth of meals.