a+b+c=148
[tex]a = \frac{b + c}{3} [/tex]
b=c+11
[tex]a = \frac{c + 11 + c}{3} = \frac{2c + 11}{3} [/tex]
[tex] \frac{2c + 11}{3} + c + 11 + c = 148[/tex]
[tex] \frac{2c + 11}{ 3} + 2c + 11 = 148[/tex]
[tex] \frac{2c + 11}{3} + \frac{3(2c + 11)}{3} = \frac{148 \times 3}{3} [/tex]
[tex]2c + 11 + 3(2c + 11) = 148 \times 3[/tex]
[tex]4(2c + 11) = 148 \times 3[/tex]
[tex]2c + 11 = \frac{148 \times 3}{4} [/tex]
2c+11=37×3
2c+11=111
2c=111-11
2c=100
c=100:2
c=50
b=c+11=50+11=61
[tex]a = \frac{b + c}{3} = \frac{61 + 50}{3} = \frac{111}{3} = 37[/tex]