Mrs. Sanders had 80 coins. Some of them were 1-dollar coins, and the rest were 50-CE coins. The total amount added up to $50. How many coins of each kind were there​

Step-by-step explanation:

Let +a+ = number of $1 coins

Let +b+ = number of $.50 coins

(1) +a+%2B+b+=+80+

(2) +1%2Aa+%2B+.5%2Ab+=+50+

(1) +b+=+80+-+a+

Substitute this into (2)

(2) a+%2B+.5%2A%28+80+-+a+%29+=+50+

(2) +a+%2B+40+-+.5a+=+50+

(2) +.5a+=+50+-+40

(2) +.5a+=+10+

(2) +a+=+20

and, since

(1) +a+%2B+b+=+80+

(1) +b+=+60+

There are 20 $1 coins and 60 $.50 coins

check:

(2) +1%2A20+%2B+.5%2A60+=+50+

(2) +20+%2B+30+=+50+

(2) +50+=+50+

step-by-step explanation: