填空。{#blank#}1{#/blank#}+ {#blank#}2{#/blank#} = {#blank#}3{#/blank#}
{#blank#}4{#/blank#}+ {#blank#}5{#/blank#} = {#blank#}6{#/blank#}
{#blank#}7{#/blank#}- {#blank#}8{#/blank#} = {#blank#}9{#/blank#}
{#blank#}10{#/blank#}- {#blank#}11{#/blank#} = {#blank#}12{#/blank#}