\starttext

\placeformula[whocares:1] \startformula x = \text{yes whocares:1} \stopformula
\placeformula[whocares:2] \startformula x = \text{yes whocares:2} \stopformula
\placeformula[-]          \startformula x = \text{nop minus} \stopformula
\placeformula[+]          \startformula x = \text{yes plus} \stopformula
\placeformula             \startformula x = \text{yes none} \stopformula

\in{whocares:1}[whocares:1]
\in{whocares:2}[whocares:2]

\placeformula
    \startsubformulas[whocares:3]% 1a 1b 1c 1d
        \startformulas
            \startformula \startalign
                \NC 1 \NC = \text{nop} \NR
                \NC 2 \NC = \text{yes plus} \NR[+]
            \stopalign \stopformula
            \startformula \startalign
                \NC 3 \NC = \text{yes whocares:4} \NR[whocares:4]
                \NC 4 \NC = \text{nop} \NR[-]
            \stopalign \stopformula
       \stopformulas
    \stopsubformulas

\in{whocares:3}[whocares:3]
\in{whocares:4}[whocares:4]

\startsubformulas[eq:sub1]
    \placeformula
        \startformula
            \startalign
                \NC a_1 x + b_1 y \NC = c_1 \NR[eq:11]
                \NC a_2 x + b_2 y \NC = c_2 \NR[eq:12]
                \NC a_2 x + b_2 y \NC = c_2 \NR[eq:13]
            \stopalign
        \stopformula
\stopsubformulas

\in{eq:11}[eq:11]
\in{eq:12}[eq:12]
\in{eq:13}[eq:13]

\placeformula
    \startformula
        \startsubformulas[eq:sub2]
            \startalign
                \NC a_1 x + b_1 y \NC = c_1 \NR[eq:21]
                \NC a_2 x + b_2 y \NC = c_2 \NR[eq:22]
                \NC a_2 x + b_2 y \NC = c_2 \NR[eq:23]
            \stopalign
        \stopsubformulas
    \stopformula

\in{eq:21}[eq:21]
\in{eq:22}[eq:22]
\in{eq:23}[eq:23]

\placeformula
    \startformula
        \startalign
            \NC a_1 x + b_1 y \NC = c_1 \NR[eq:31]
            \NC a_2 x + b_2 y \NC = c_2 \NR[eq:32]
            \NC a_2 x + b_2 y \NC = c_2 \NR[eq:33]
        \stopalign
    \stopformula

\in{eq:31}[eq:31]
\in{eq:32}[eq:32]
\in{eq:33}[eq:33]

\stoptext
