If called as `solve_sys(lhs, vars)`

the roots are found.
If called as `solve_sys(lhs, rhs, vars)`

the solutions to `lhs = rhs`

for `vars`

are found.

`solve_sys(lhs, rhs, vars)`

- lhs
Equation (or equations as row vector/1xn matrix)

- rhs
Equation (or equations as row vector/1xn matrix)

- vars
vector of variable names or symbols

A list with solutions (with class `caracas_solve_sys_sol`

for compact printing), each element containing a named list of the variables' values.

```
if (has_sympy()) {
x <- symbol('x')
exp1 <- 2*x + 2
exp2 <- x
solve_sys(cbind(exp1), cbind(exp2), x)
x <- symbol("x")
y <- symbol("y")
lhs <- cbind(3*x*y - y, x)
rhs <- cbind(-5*x, y+4)
sol <- solve_sys(lhs, rhs, list(x, y))
sol
}
#> Solution 1:
#> x = 2/3
#> y = -10/3
#> Solution 2:
#> x = 2
#> y = -2
```