Решебник по математике 5 класс Мерзляк ФГОС Решаем устно параграф 12

\[\boxed{\mathbf{1.\ }}\]

\[48 + 14 = 62\]

\[62 - 23 = 39\]

\[38 - 18 = 21\]

\[21 + 79 = 100\]

\[\boxed{\mathbf{2.\ }}\]

\[1)\ x + 13 = 28\]

\[x = 28 - 13\]

\[x = 15.\]

\[2)\ 20 - x = 12\]

\[x = 20 - 12\]

\[x = 8.\]

\[3)\ x - 11 = 79\]

\[x = 79 + 11\]

\[x = 90.\]

\[4)\ 10 + x = 28\]

\[x = 28 - 10\]

\[x = 18.\]

\[\boxed{\mathbf{3.\ }}\]

\[1)\ 2x - 3 = 7\]

\[2x = 7 + 3\]

\[2x = 10\]

\[x = 10\ :2\]

\[x = 5.\]

\[2)\ x + 20 = 20 + x\]

\[x - любое\ число.\]

\[3)\ x \cdot x \cdot x + 25 = 150\]

\[x = 5.\]

\[4)\ x + 12 = 22 - x\]

\[x = 5.\]

\[\boxed{\mathbf{4.\ }}\]

\[У\ Маши\ стало\ больше\ на\ \]

\[16\ конфет.\]