Question

Help me substitution method define variables

Answer 1

$\left \{ {{S=14+L} (I) \atop {S+L=124}(II)} \right.$

Substitute (I) into (II), we have:
$S+L=124$
$(14+L)+L=124$
$14 + 2L = 124$
$2L = 124 - 14$
$2L = 110$
$L = \frac{110}{2}$
$\boxed{L = 55}$

Replace (II) in (I), we have:
$S=14+L$
$S = 14+ 55$
$\boxed{S = 69}$

Answer:
each student sell: 
Lori = 55 pizzas
Steve = 69 pizzas