4a+5c+4u = 49 and 4a+2c+2u = 28 and 4a+3c+6u = 45 Solve each system of equations

4a+2c+2u = 28

4a-4a+2c+2u = 28-4a

2c-2c+2u = 28-4a-2c

2u = 28-4a-2c

2u/2 = 28-4a-2c/2

u=14-2a-c

4a+5c+4u = 49

4a+5c+4(14-2a-c) = 49

4a+5c+4(14) (4)(-2a) (4)(-c) = 49

4a+5c+56-8a-4c=49

c+56-4a=49

c+56-4a-56=49-56

c-4a=-7

c-4a+4a=-7+4a

c=4a-7

u=14-2a-c

u=14-2a-4a-7

u=7-6a

4a+3c+6u = 45

4a+3(4a-7)+6(7-6a) = 45

4a+3(4a) (3)(-7)+6(7) (6)(-6a) = 45

4a+12a-21+42-36a=45

21-20a=45

21-20a-21=45-21

-20a=24

-20a/-20=24/-20

a=-1.2

u=7-6a

u=7-6(-1.2)=7--7.2=7+7.2=14.2

c=4a-7

c=4(-1.2)-7=-4.8-7=-11.8