A hardware supplier manufactors three kinds of clamps, tye a,b,c. Production restrictions force it to make 20 more type c clamps that the total of the other types and three times as many type b as type a clamps. The shop must produce 500 clamps per day. How many of each type are made per day.

We know that total production , A+B+C =500 units.
We know that B=2A
We know that A+B +20 = C
We need to solve for A

If A+B+C =500 units, then by substitution, A + [2A] + [A+ 2A + 20]=500
A+2A+3A +20=500
6A=500-20 so 6A=480 and therefore A=80

So A=80 units, B=160 units and C=260 units
80+160+260=500 units