SimpleSpeak: multiline

case_1: f of x is equal to; 3 cases, case 1; negative 1 if x; is less than 0; case 2; 0 if x, is equal to 0; case 3; 1 if x, is greater than 0;

f (x) = {\begin{matrix} - 1 if x < 0 \\ 0 if x = 0 \\ 1 if x > 0 \end{matrix}

equation_1: 2 equations, equation 1; x plus y, is equal to, 7; equation 2; 2 x plus 3 y, is equal to, 17;

\begin{matrix} x + y & = & 7 \\ 2 x + 3 y & = & 17 \end{matrix}