(2×a×5-2×15):5=10, a-35=13x5 a-35=65 a= 100
312-34:X-258=50 312-34:x=50+258 312-34:x=308 34:x=312-308 34:x=4 x=34 * 4 =136
(a+13)x3+20=110 3xa+39+20=110 3xa +59=110 3xa=110-59 3xa=51 a = 17
(7×a-5+12):7=7 7xa-5+12=49 7xa=49-12+5 7xa=42 a =6
(2 x a x5 -2x15)