Question 1031350
X-number of ones
Y-number of fives
Z-number of twenties
1.{{{X+Y+Z=30}}}
.
.
{{{Z=9+X}}}
2.{{{-X+Z=9}}}
.
.
3.{{{X+5Y+20Z=351}}}
Use Cramer's rule,
{{{A=(matrix(3,3,
1,1,1,
-1,0,1,
1,5,20))}}}
{{{abs(A)=11}}}
.
.
{{{A[X]=(matrix(3,3,
30,1,1,
9,0,1,
351,5,20))}}}
{{{abs(A[X])=66}}}
.
.
{{{A[Y]=(matrix(3,3,
1,30,1,
-1,9,1,
1,351,20))}}}
{{{abs(A[Y])=99}}}
.
.
{{{A[Z]=(matrix(3,3,
1,1,30,
-1,0,9,
1,5,351))}}}
{{{abs(A[Z])=165}}}
.
.
{{{X=abs(A[X])/abs(A)=66/11=6}}}
{{{Y=abs(A[Y])/abs(A)=99/11=9}}}
{{{Z=abs(A[Z])/abs(A)=165/11=15}}}