Answer:
S(x) = 360 + 0.025x
Step-by-step explanation:
Let Sm be Salary per month
Let x be sales per month
Let S(x) be savings per month
Sm = 1800 + 0.1x
where 0.1x is the commission on sales
S(x) = 20% of 1800 + 25% of 0.1x
20% of 1800 = 20/100 * 1800 = 360
25% of 0.1x = 25/100 * 0.1x = 0.025x
Therefore,
S(x) = 360 + 0.025x