The four angles of a quadrilateral are ${\mathrm{A}}_1, {\mathrm{A}}_2, {\mathrm{A}}_3$ and ${\mathrm{A}}_4$. The sum of ${\mathrm{A}}_1$ and ${\mathrm{A}}_2$ is greater than ${\mathrm{A}}_3$ by $20°$ and ${\mathrm{A}}_4$ is greater than ${\mathrm{A}}_3$ by $70°$. What is the sum of ${\mathrm{A}}_1$ and ${\mathrm{A}}_2$?