Answer:
a = 16
b = 10
c = 19
d = 3
Step-by-step explanation:
For a, we know that 60 is 12+a+a+a, and to find what a is, we subtract 12 from 60, so that 48=3a, so 48 is a times 3. dividing 48 by 3 gives a=16
For b, we know that 60 is 4(b+5), dividing both sides by 4, 15=b+5. Subtracting 5 from both sides, b=10
For c, we know that a+b+c=3(b+5), or 16+10+c=45, subtracting 26 from each side, c=19
For d, we know that 3c+d=60, or (19*3)+d=60. simplifying, 57+d=60. subtraction 57 from each side gives d=3
